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Objective: We identified the associated factors and compared the survival times of feline hyperthyroidism (FHT) between thyroidectomy and methimazole alone., Methods: The medical records of 41 cats diagnosed with new-onset hyperthyroidism were retrospectively reviewed. The cats were categorized into the thyroidectomy (n = 15) and methimazole (26) treatment groups. Survival analyses using the Kaplan-Meier method, log-rank test, and Cox proportional hazards models were conducted to compare the time to the selected outcomes., Results: Univariate analysis revealed that survival time was significantly longer with thyroidectomy than with methimazole (P < .001). Multivariate analyses revealed thyroidectomy as an independent prognostic factor for good outcomes (hazard ratio, 0.209; 95% CI, 0.073 to 0.601; P = .004). The recurrence rate was significantly lower in cats that underwent thyroidectomy than in those that received methimazole alone (P = .011)., Clinical Relevance: Compared with methimazole alone, thyroidectomy was associated with a longer survival time in FHT and can be considered an irreversible treatment modality in settings where radioisotopes are not available.

Research on modulation of iodine uptake by thyroid cells could help improve radioiodine treatment of dogs with thyroid tumors. The aim of this study was to characterize the immunohistochemical expression of thyroid transcription factor-1 (TTF-1), thyroglobulin, thyrotropin receptor (TSHR), sodium iodide symporter (NIS), pendrin, thyroid peroxidase (TPO), vimentin, and Ki-67 in follicular cell thyroid carcinomas (FTCs) and medullary thyroid carcinomas (MTCs), and to compare protein expression between FTC causing hyperthyroidism and FTC of euthyroid dogs. Immunohistochemistry was performed in 25 FTCs (9 follicular, 8 follicular-compact, and 8 compact) and 8 MTCs. FTCs and MTCs were positive for TTF-1, and expression was higher in FTCs of euthyroid dogs compared with FTCs of hyperthyroid dogs ( P = .041). Immunolabeling for thyroglobulin was higher in follicular and follicular-compact FTCs compared with compact FTCs ( P = .001), while vimentin expression was higher in follicular-compact FTCs compared with follicular FTCs ( P = .011). The expression of TSHR, NIS, pendrin, and TPO was not significantly different among the different subtypes of FTCs or between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. TSHR, NIS, pendrin, and TPO were also expressed in MTCs. Ki-67 labeling index was comparable between FTCs and MTCs, and between FTCs causing hyperthyroidism and FTCs in euthyroid dogs. Proteins of iodine transport were also expressed in canine MTCs, which could have implications for diagnosis and treatment. The different expression of thyroglobulin and vimentin between FTC histological subtypes could reflect variations in tumor differentiation., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Health-related quality-of-life (HRQoL) assessment tools are becoming increasingly important for the assessment of diseases in veterinary medicine., Objectives: To develop a tool to assess the HRQoL of hyperthyroid cats and their owners., Animals: Cats with hyperthyroidism (n = 229) and without hyperthyroidism (n = 322)., Methods: Cross-sectional study design. A preliminary list of 28 questions relating to the HRQoL of hyperthyroid cats and the influence their cat's disease might have on owners was created. Each question consisted of 2 subquestions: (1) "how often does the item apply"; (2) "how strongly does the item affect HRQoL." The questionnaire was refined based on statistical analysis, including Mann-Whitney-U tests on each item, comparing the results from cats with and without hyperthyroidism. Internal consistency and reliability of the questions were measured by Cronbach's alpha (α). P < .05 was considered significant., Results: Overall, 25/28 questions were retained within the final HRQoL tool, which had an excellent internal consistency (α = .92). The tool produced a score between 0 and 382 (lower scores meaning better HRQoL). The median HRQoL score was 87.5 (range, 2-348) for cats with hyperthyroidism, and 27 (range, 0-249) for cats without (P < .001), suggesting the HRQoL was poorer in hyperthyroid cats., Conclusions and Clinical Importance: This validated HRQoL tool is useful to reliably quantify the influence of hyperthyroidism on the quality-of-life of affected cats and their owners. In the future, it could be considered of assistance in the clinical assessment of cats with hyperthyroidism., (© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Hyperthyroid cats commonly have systemic hypertension, with a reported prevalence of 7% to 48%. Although hypertension might be expected to resolve once treatment restores euthyroidism, it can persist or only first develop after treatment., Objectives: To determine the proportion of hyperthyroid cats with hypertension (systolic blood pressure [SBP] ≥160 mm Hg), persistence or first development of hypertension after successful radioiodine treatment, and correlation of post-treatment hypertension with azotemia or hypothyroidism., Animals: Four hundred one hyperthyroid nonazotemic cats were included in the study., Methods: Prospective, cross-sectional and before-and-after studies. All hyperthyroid cats had SBP measured by Doppler; 255 had SBP rechecked 6 months after successful radioiodine ( 131 I) treatment., Results: Of untreated hyperthyroid cats, 108/401 (27%) were hypertensive. A higher proportion of hypertensive cats were nervous/excited compared with normotensive cats (47% vs 12%; P < .001). Of the initially hypertensive cats, 87/108 cats were reexamined after 131 I treatment; 43/87 (49%) cats normalized SBP, whereas 44/87 (51%) remained hypertensive. Of the initially normotensive cats, 16/168 (9.5%) first developed hypertension after successful 131 I treatment. 7/60 (12%) of the 131 I-treated hypertensive cats were azotemic and 9/60 (15%) were hypothyroid. A higher proportion of cats remaining hypertensive had nervous/excited demeanor than did normotensive cats (50% vs 17%; P < .001)., Conclusions/clinical Importance: Hypertension, when present, resolves in many hyperthyroid cats after successful treatment. Hyperthyroid cats uncommonly develop new hypertension after treatment. Persistent or newly detected hypertension was unrelated to azotemia or iatrogenic hypothyroidism. More frequently perceived nervousness/anxiety in radioiodine-treated hypertensive cats suggests that many of these cats might have "situational" hypertension, as hyperthyroid-induced hypertension should resolve after treatment., (© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Hyperthyroidism in humans is associated with a hypercoagulable state and an increased risk of thromboembolism., Objective: To evaluate hemostatic variables in hyperthyroid and euthyroid cats with the hypothesis that hyperthyroid cats will have evidence of altered hemostasis consistent with a potential hypercoagulable state., Animals: Client-owned hyperthyroid (n = 16) and euthyroid (n = 15) cats over 8 years of age., Methods: Prospective observational study. Hyperthyroid and euthyroid cats were enrolled. Rotational thromboelastometry (ROTEM), whole-blood platelet impedance aggregometry (WBPIA) and a point-of-care viscoelastic coagulation monitor (VCM-Vet) were performed immediately after minimally traumatic venipuncture under sedation., Results: Hyperthyroid cats had significantly higher values for variables as assessed by VCM-Vet: A10 (34 [17-47] vs 25 [17-38], P = .003); A20 (39.5 [23-55] vs 31 [21-45], P = .003); and MCF (41 [24-58] vs 35 [22-49], P = .03). Hyperthyroid cats had significantly different values versus the euthyroid cohort as assessed by different ROTEM channels: increased A10, INTEM (61.5 [39-75] vs 54 [23-66], P = .007) and FIBTEM (18 [10-35] vs 13 [2-27], P = .01); increased A20, INTEM (68 [45-78] vs 61 [30-70], P = .006) and FIBTEM (17 [10-34] vs 11 [2-25], P = .002); increased MCF, EXTEM (72 [65-81] vs 69 [34-78], P = .04), INTEM (70 [45-85] vs 62 [35-71], P = .01) and FIBTEM (18 [13-37] vs 14 [3-27], P = .02); increased alpha angle, EXTEM (80 [68-85] vs 76 [41-84], P = .01); shortened CT, EXTEM (52.5 [29-73] vs 60 [52-92], P = .003) and FIBTEM (52.5 [16-75] vs 65 [53-165], P = .001); and decreased ML, FIBTEM (20 [1-36] vs 33 [19-59], P <.001). No significant differences were found with WBPIA., Conclusions and Clinical Importance: The hyperthyroid cats in this study had evidence of altered hemostasis as assessed by 2 viscoelastic methodologies, and characterized by increased clot amplitude, firmness, and faster coagulation times vs euthyroid controls., (© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objective: Clinicians commonly use thyroid-stimulating hormone (TSH) concentrations to diagnose thyroid disorders in humans and dogs. In cats, canine TSH chemiluminescent immunoassays (CLIA) assays are commonly used to measure TSH, but these TSH-CLIAs cannot measure low TSH concentrations (< 0.03 ng/mL) and therefore cannot distinguish between low-normal concentrations and truly low TSH concentrations (characteristic of hyperthyroidism). Our aim was to evaluate a novel TSH assay based on bulk acoustic wave (BAW) technology that has lower functional sensitivity (0.008 ng/mL) than TSH-CLIAs., Animals: 169 untreated hyperthyroid cats, 53 cats treated with radioiodine (131I), 12 cats with chronic kidney disease (CKD), and 78 clinically healthy cats., Methods: Serum concentrations of T4, TSH-CLIA, and TSH-BAW were measured in all cats. Untreated hyperthyroid cats were divided into 4 severity groups (subclinical, mild, moderate, and severe), whereas 131I-treated cats were divided into euthyroid and hypothyroid groups., Results: Test sensitivity, specificity, and positive predictive value for identifying hyperthyroidism were higher for TSH-BAW (90.5%, 98.9%, and 86.9%) than TSH-CLIA (79.9%, 76.7%, and 21.7%; P < .001). Test sensitivity for identifying 131I-induced hypothyroidism was only 45.5% for T4 versus 100.0% for both TSH-CLIA and TSH-BAW (P = .03), whereas TSH-BAW had a higher positive predictive value (100%) than did either TSH-CLIA (81.2%) or T4 (71.9%)., Clinical Relevance: Serum TSH-BAW alone or together with T4 is a highly sensitive and specific diagnostic test for evaluating feline hyperthyroidism and iatrogenic hypothyroidism. Finding low serum TSH-BAW concentrations is most useful for diagnosing subclinical and mild hyperthyroidism, in which serum T4 remains within or only slightly above the reference interval.

Hyperthyroidism is considered the most common endocrinopathy in middle-aged and old cats. The increased level of thyroid hormones influences many organs, including the heart. Cardiac functional and structural abnormalities in cats with hyperthyroidism have indeed been previously described. Nonetheless, myocardial vasculature has not been subjected to analysis. Also, no comparison with hypertrophic cardiomyopathy has been previously described. Although it has been shown that clinical alterations resolve after the treatment of hyperthyroidism, no detailed data have been published on the cardiac pathological or histopathological image of field cases of hyperthyroid cats that received pharmacological treatment. The aim of this study was to evaluate the cardiac pathological changes in feline hyperthyroidism and to compare them to alterations present in cardiac hypertrophy due to hypertrophic cardiomyopathy in cats. The study was conducted on 40 feline hearts divided into three groups: 17 hearts from cats suffering from hyperthyroidism, 13 hearts from cats suffering from idiopathic hypertrophic cardiomyopathy and 10 hearts from cats without cardiac or thyroid disease. A detailed pathological and histopathological examination was performed. Cats with hyperthyroidism showed no ventricular wall hypertrophy in contrast to cats with hypertrophic cardiomyopathy. Nonetheless, histological alterations were similarly advanced in both diseases. Moreover, in hyperthyroid cats more prominent vascular alterations were noted. In contrast to hypertrophic cardiomyopathy, the histological changes in hyperthyroid cats involved all ventricular walls and not mainly the left ventricle. Our study showed that despite normal cardiac wall thickness, cats with hyperthyroidism show severe structural changes in the myocardium.

Objectives: Annual health screening is recommended in elderly cats to allow the early detection of conditions such as chronic kidney disease (CKD) and hyperthyroidism. Nevertheless, age-specific reference intervals (RIs) for renal and thyroid parameters in this population are lacking. The aim of this study was to determine age-specific RIs for selected serum and urine biomarkers related to CKD and hyperthyroidism, namely serum creatinine (sCr), symmetric dimethylarginine (SDMA), phosphate (P), total calcium (tCa), total thyroxine (TT4), urinary protein:creatinine ratio (UPC) and urine specific gravity (USG). These RIs were established for elderly cats (aged ⩾7 years) in general, as well as for mature adult cats (aged 7-10 years) and senior cats (aged >10 years) separately., Methods: A prospective study was conducted on client-owned cats aged ⩾7 years and considered healthy by their owners. The cats were screened to rule out metabolic and systemic diseases by means of a thorough history, complete physical examination, blood examination and urinalysis. The data from 206 healthy elderly cats (134 mature adult and 72 senior cats) were included. Age-appropriate RIs were determined following the guidelines of the American Society of Veterinary Clinical Pathology and compared with existing laboratory RIs., Results: Clinically relevant differences between the age-specific RI and the laboratory RI were found for several variables. Compared with the laboratory RI, the upper limit of the RI for cats aged ⩾7 years was lower for sCr, TT4 and P, and higher for SDMA. The lower limit of the age-appropriate RI was lower for USG. The new RI was almost identical to the existing laboratory RI for tCa and UPC., Conclusions and Relevance: Using age-specific RIs for renal and thyroid biomarkers in mature adult and senior cats has important clinical consequences for the interpretation of health screening results in elderly cats. This confirms the need to adapt laboratory RIs to the specific animal population for which the RI will be used., Competing Interests: Conflict of interestThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Hyperthyroid cats often have urine specific gravity (USG) values <1.035. It remains unclear how USG changes after treatment, if USG can be used to predict azotemia after treatment, or how iatrogenic hypothyroidism influences USG values., Objectives: To determine the proportion of hyperthyroid cats with USG <1.035 vs ≥1.035; if USG changes after treatment; and whether USG <1.035 correlated with unmasking of azotemia or hypothyroidism., Animals: Six hundred fifty-five hyperthyroid cats treated with radioiodine; 190 clinically normal cats., Methods: Prospective, before-and-after study. Hyperthyroid cats had serum thyroxine, thyroid-stimulating hormone, and creatinine concentrations, and USG measured before and 6 months after successful treatment with radioiodine., Results: Of untreated hyperthyroid cats, USG was ≥1.035 in 346 (52.8%) and <1.035 in 309 (47.2%). After treatment, 279/346 (80.6%) maintained USG ≥1.035, whereas 67/346 (19.4%) became <1.035; 272/309 (88%) maintained USG <1.035, whereas 37/309 (12%) became ≥1.035. Only 22/346 (6.4%) with USG ≥1.035 developed azotemia after treatment, compared with 136/309 (44%) with <1.035 (P < .001). Of cats remaining nonazotemic, 38% had USG <1.035, compared with 20% of normal cats (P < .001). The 137 cats with iatrogenic hypothyroidism had lower USG after treatment than did 508 euthyroid cats (1.024 vs 1.035), but USGs did not change after levothyroxine supplementation. USG <1.035 had high sensitivity (86.1%) but moderate specificity (65.2%) in predicting azotemia after treatment., Conclusions and Clinical Importance: Hyperthyroidism appears not to affect USG in cats. However, cats with evidence of sub-optimal concentrating ability before radioiodine treatment (USG < 1.035) are more likely to develop azotemia and unmask previously occult chronic kidney disease. Iatrogenic hypothyroidism itself did not appear to affect USG values., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objective: Apply the 3-site echocardiographic metrics utilized to assess pulmonary hypertension (PH) probability in dogs and humans to feline echocardiographic examinations to investigate the translatability of this scheme and subsequent enhancement of detection of PH in cats., Animals: 27 client-owned cats (euthyroid [n = 11] and hyperthyroid [16])., Methods: This was a single-center, prospective, observational case-control study. Demographic, physical examination, and echocardiographic data from hyperthyroid and euthyroid cats were compared via Fisher exact test and Kruskal-Wallis test., Results: Hyperthyroid versus euthyroid cats had significantly greater right atrial area index values and were more likely to have late-peaking main pulmonary artery pulsed-wave flow profiles. Two hyperthyroid cats had measurable tricuspid regurgitation tracings (one with a high probability of PH and another with a low probability of PH)., Clinical Relevance: Hyperthyroid cats demonstrated altered pulmonary arterial hemodynamics and lacked consistent intermediate or high probability of PH. The 3-site echocardiographic metrics scheme is applicable for the evaluation of right-sided cardiac and pulmonary arterial hemodynamics in cats. Further research is needed to determine reference ranges in larger populations of healthy cats and those with high clinical suspicion for PH.

Chickens experience rapid change in their physiology and metabolism during hatching. We propose that thyroid hormones play a major role in regulating the developmental changes associated with attaining endothermy. To better understand the role thyroid hormones play in hatch timing and development of thermogenic capacity and metabolic rate we manipulated plasma thyroid hormone levels in chicken embryos beginning at 80% development (day 17 of a 21-day incubation) with either a single dose of triiodo-L-thyronine (T 3 ) or the thyroperoxidase inhibitor methimazole (MMI). Manipulation of thyroid hormones altered the timing of hatching, accelerating hatching under hyperthyroid conditions, and prolonging hatching with hypothyroid conditions. Effect sizes comparisons of morphological variables between treatment groups revealed larger heart and body masses in hyperthyroid 1-day post hatch animals. Thyroid hormone manipulation influenced the thermal neutral zone for O 2 consumption and body temperature during gradual cooling from 35 to 15 °C of externally pipped embryos and 1-day post hatch chicks. Hyperthyroid EP animals had a wider thermal neutral zone during cooling when compared to control animals. At the temperatures tested, the hypothyroid animals did not exhibit a thermal neutral zone. Similar differences between treatments in the breadth of the thermal neutral zone carried through to 1-day post hatch chickens. These findings suggest that thyroid manipulations influence the timing and development of the animal's thermogenic response to cooling., Competing Interests: Declaration of competing interest There are no competing interests to this publication., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Glutamate dehydrogenase (GLDH), a key enzyme in amino acid oxidation and urea production, is mainly derived from the liver and its activity may increase with hepatocellular necrosis. Feline hyperthyroidism is associated with elevated serum activities of various enzymes, but the pattern of serum GLDH activity has not been reported, to our knowledge. Feline clinical biochemistry results from 2 commercial diagnostic laboratories were reviewed retrospectively to assess changes in serum GLDH activity in cats with significantly elevated serum total T4 concentrations, which is highly suggestive of hyperthyroidism. A total of 2,773 records were analyzed, of which 2,370 (85%) had normal total T4 (≤50 nmol/L) and 403 (15%) had increased total T4 (≥60 nmol/L) concentrations. Among cats with an increased total T4 concentration, 26.5% had increased serum GLDH activity. All cats with increased GLDH activity also had increased serum ALT activity. In 42.9% of cats, ALT activity was increased, but GLDH activity was normal. In 30.5% of cats, both serum GLDH and ALT activities were within RIs. The fold-increase of GLDH activity was almost half of the ALT fold-increase. Although serum GLDH activity increased in some cats with hyperthyroidism, serum ALT activity increased more frequently and to a greater extent.

Objectives: The aims of this study were to evaluate concentrations of symmetric dimethylarginine (SDMA) in hyperthyroid cats before and after radioiodine treatment, and to compare results with other variables used to assess kidney function in cats (creatinine, urine specific gravity [USG] and glomerular filtration rate [GFR] measured by renal scintigraphy)., Methods: Thirteen cats diagnosed with hyperthyroidism based on clinical signs and increased serum total thyroxine (TT4) were included in this prospective study. Study design included physical examination, complete blood count, serum chemistry, TT4, urinalysis and SDMA before treatment (T0) and at 1 month (T1) and 3 months post-treatment (T3). GFR was quantified by renal scintigraphy at T0 and T3., Results: Median GFR decreased significantly from baseline (3.18 ml/kg/min; range 1.35-4.87) at T3 (2.22 ml/kg/min; range 1.81-3.42 [ P  = 0.005]). While median creatinine and serum urea nitrogen increased post-treatment (creatinine: T0 = 0.8 mg/dl [range 0.4-1.1], T1 = 1.3 mg/dl [range 0.9-2]; T3 = 1.65 mg/dl [range 0.8-2.8]; P <0.001; serum urea nitrogen: T0 = 23 mg/dl [range 15-26]; T1 = 27 mg/dl [range 20-40]; T3 = 27.5 mg/dl [range 20-36]; P <0.001), SDMA and USG did not change significantly (SDMA: T0 = 11 µg/dl [range 7-15]; T1 = 12 µg/dl [range 6-16]; T3 = 10.5 µg/dl [range 8-21]; P  = 0.789; USG: T0 = 1.030 [range 1.011-1.059]; T1 = 1.035 [range 1.012-1.044]; T3 = 1.030 [range 1.007-1.055]; P  = 0.792)., Conclusions and Relevance: Our data suggest that factors other than GFR may affect serum SDMA in hyperthyroid cats and that SDMA does not offer an advantage over other biomarkers traditionally used to predict changes in renal function following radioiodine therapy.

Objectives: The aim of this study was to estimate the prevalence of hypersomatotropism (HST) and hyperthyroidism in cats with diabetes mellitus (DM) from referral centers in Buenos Aires, Argentina., Methods: This was a prospective study. Systematic screening of serum insulin-like growth factor 1 (IGF-1) and total thyroxine was performed in all cats diagnosed with DM at referral centers in Buenos Aires between February 2020 and February 2022., Results: In total, 154 diabetic cats were evaluated (99 males and 55 females; median age 12 years [range 3-21]; mean body weight 5 kg [range 2-12]). Altogether, there were 115 (75%) domestic shorthairs and one domestic longhair; the remaining 38 cats were purebred (mainly Siamese, n = 25 [16%]). Twenty (12.9%) cats had IGF-1 concentrations >1000 ng/ml, and three (1.9%) had IGF-1 concentrations between 800 and 1000 ng/ml along with pituitary enlargement on CT, resulting in a 14.9% HST prevalence rate in diabetic cats. Intracranial imaging was performed in all cats with HST; median pituitary dorsoventral height was 5.8 mm (range 3.1-9.5). Fourteen of 23 (61%) cats had phenotypic changes consistent with acromegaly at the time of diagnosis of HST. Four of 154 (2.5%) cats had concurrent hyperthyroidism., Conclusions and Relevance: To date, this is the first study outside of Europe to have evaluated the prevalence of HST and hyperthyroidism in cats with DM. In Buenos Aires referral centers, feline HST is the most common concurrent endocrinopathy in cats with DM but with a lower prevalence than has previously been reported. Hyperthyroidism is a rare concurrent endocrinopathy in diabetic cats from referral centers in Buenos Aires.

Objectives: Radioiodine ( 131 I) therapy is the most appropriate treatment option for many hyperthyroid cats, as it is minimally invasive and often curative. Nevertheless, 131 I treatment is not always pursued by owners. Hence, it is important to obtain more insight into owner satisfaction during and after 131 I treatment, and their decision-making process. In this study, we describe the characteristics of owners and their hyperthyroid cats referred for 131 I therapy, and determine owners' motivation and how they experienced the 131 I treatment of their cat., Methods: A survey was sent to owners whose cats underwent 131 I therapy (n = 1071) between 2010 and 2017 at Ghent University. The survey contained 35 questions with tick-box or free-text answer options concerning family situation, pet insurance, previous therapy, comorbidities, motivation for 131 I therapy and owner perception of this treatment., Results: In total, 438 owners completed 94% or more of the questionnaire. Over half of the cats (55%) had received previous medical, dietary or surgical treatment. Motivations for changing the initial therapy to 131 I therapy included difficulties in administering medication (31%), insufficient improvement in clinical signs (23%), side effects (16%) and following the referring veterinarian's advice (16%). Almost a fifth of owners (18%) were not informed about the existence of 131 I therapy by their veterinarian and found information on 131 I treatment online or through friends. Hospitalising their cat was very distressing for 17% of owners. Most owners (92%) were satisfied with the treatment. Reasons for dissatisfaction were insufficient communication, iatrogenic hypothyroidism, persistent hyperthyroidism and comorbidities post-treatment., Conclusions and Relevance: Our study stresses the importance of communication regarding the possible outcome of 131 I treatment, the importance of managing underlying comorbidities before treatment and anticipating the stress of owners during their cat's hospitalisation period. The results of this study could help in improving client communication when advising on 131 I treatment.

Diagnosis of thyroid and adrenal disease can be confusing. Whereas the definitive diagnosis of hyperthyroidism and hypoadrenocorticism are relatively straightforward, hypothyroidism and naturally occurring Cushing's syndrome (NOCS) are more complicated. In a patient with compatible clinical signs, a single increased tT 4 is enough to confirm hyperthyroidism, but a low tT 4 alone is never enough to confirm hypothyroidism. A flatline result (post-stimulation cortisol <2 ug/dL) on an ACTH stimulation test (ACTHst) confirms hypoadrenocorticism, but not all dogs with NOCS have increased ACTHst results. This article explains which diagnostics should be pursued for these endocrinopathies, and how to interpret them., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Approximately 75% of hyperthyroid cats lose muscle mass as accessed with a muscle condition scoring (MCS) system. After treatment, MCS improves as the cats regain muscle mass., Objectives: To quantify the degree of muscle loss in hyperthyroid cats using ultrasonography and evaluate changes in muscle mass after treatment., Animals: Forty-eight clinically normal cats and 120 cats with untreated hyperthyroidism, 75 of which were reevaluated after radioiodine-131 therapy., Methods: Prospective cross-sectional and before-after studies. All cats underwent ultrasonography and measurement of epaxial muscle height (EMH), with subsequent calculation of vertebral and forelimb epaxial muscle scores (VEMS and FLEMS). A subset of hyperthyroid cats underwent repeat muscle imaging 6 months after treatment., Results: Untreated hyperthyroid cats had a lower EMH than did clinically normal cats (median [25th-75th percentile], 0.98 [0.88-1.16] cm vs 1.34 [1.23-1.58] cm, P < .001). Seventy-seven (64.2%) untreated cats had subnormal EMH. Similarly, compared to normal cats, hyperthyroid cats had lower VEMS (0.93 [0.84-1.07] vs 1.27 [1.18-1.39], P < .001) and FLEMS (1.24 [1.10-1.35] vs 1.49 [1.39-1.63], P < .001). After treatment, EMH increased (1.03 [0.89-1.03] cm to 1.33 [1.17-1.41] cm, P < .001), with abnormally low EMH normalizing in 36/41 (88%). Both VEMS (0.94 [0.87-1.10] to 1.21 [1.10-1.31], P < .001) and FLEMS (1.31 [1.17-1.40] to 1.47 [1.38-1.66], P < .001) also increased after treatment., Conclusions and Clinical Importance: Almost two-thirds of hyperthyroid cats have abnormally low muscle mass when measured quantitatively by ultrasound. Successful treatment restores muscle mass in >85% of cats. EMH provided the best means of quantitating muscle mass in these cats., (© 2022 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objectives: Felinehyperthyroidism is the most common endocrine disease of older cats and radioiodine is considered to be the gold standard treatment. Isolation periods following treatment vary depending on both individual treatment facilities and the relevant legislation of the country; therefore, there is no recognised standardised protocol defining the length of isolation. This work describes how our institution validated that its owner restrictions met dose constraints by using a model of iodine retention to calculate the required duration and nature of owner restrictions., Materials and Methods: The retained radioactivity of cats at the point of discharge was used to simulate the radiation dose to owners in the 90 days following release. The model created was used to calculate the minimum duration of isolation for a range of administered activities and owner restrictions., Results: Using the model, it was found that when injected with the maximum dose used, 222 MBq radioiodine, it was possible to release cats after 14 days of isolation and keep owner doses below 0.30 mSv (whole-body effective dose constraint for a single radiation source) with some restrictions. It was possible to release after 23 days with no restrictions., Clinical Significance: The present study provides clinicians with a consistent and verified method in which they can calculate the isolation periods for radioiodine-treated cats., (© 2022 British Small Animal Veterinary Association.)

Objectives: Hyperthyroidism frequently affects middle-to-older-aged cats that can present with cardiorespiratory signs. The effects of hyperthyroidism on cardiac size and function have been previously documented. Anecdotally, pulmonary hyperinflation identified on thoracic radiographs may also be associated with hyperthyroidism; however, there is no literature to support this claim. The goal of this study was to determine any association between hyperthyroidism, pulmonary hyperinflation and cardiomegaly with the following hypotheses: (1) hyperthyroid cats would not have evidence of radiographic pulmonary hyperinflation compared with control cats; and (2) hyperthyroid cats were more likely to have evidence of radiographic cardiomegaly than control cats., Methods: In this retrospective case-control study, the thoracic radiographs of 52 hyperthyroid cats and 46 non-hyperthyroid cats were evaluated for subjective and objective measurements of pulmonary hyperinflation and cardiomegaly., Results: There were no statistically significant differences between hyperthyroid and non-hyperthyroid cats for any variable indicative of pulmonary hyperinflation. The mean ± SD vertebral heart score on lateral views for hyperthyroid cats was 7.75 ± 0.53 and for control cats was 7.55 ± 0.54, which was significantly different ( P  = 0.05). Among all cats, a more severe total elevation in thyroxine (T4) was correlated with a larger vertebral heart score on lateral views (Spearman's correlation coefficient = 0.23, P  = 0.02)., Conclusions and Relevance: While the results of this study suggest that hyperthyroid cats are more likely to have a larger vertebral heart score on lateral views than control cats, the clinical relevance of this finding is unclear given the large degree of overlap between hyperthyroid and non-hyperthyroid cats. In addition, among all cats, a greater total T4 elevation was weakly correlated with a larger vertebral heart score. Hyperthyroidism is not associated with radiographic pulmonary hyperinflation and is an unlikely differential for this radiographic finding.

Objectives: The aim of this study was to collect data from a substantial number of older cats having their systolic blood pressure (SBP) measured in a variety of clinical practices, to describe the findings and assess variables that affected the duration of assessment and the values obtained., Methods: An international (European-based) multicentre convenience sample survey of cats ⩾7 years of age attending veterinary clinics and having SBP measured as part of their clinical assessment. Information gathered included details of the cat, concomitant disease(s) or therapies, SBP results, device used, time taken to assess SBP and the demeanor of the cat., Results: Useable data were available from 8884 cats aged 7-26 years, from 811 clinics across 16 countries. The device used to measure SBP was Doppler in 47.4% and oscillometry in 48.5%. The demeanor of the cat was reported to be calm in 45.7%, anxious in 41.9% and nervous in 8.9%; and the duration of assessment was reported to be <5 mins in 50.4%, 5-10 minutes in 41.7% and >10 mins in 7.9%. Concomitant chronic kidney disease (CKD) was reported in 21.8%, hyperthyroidism in 12.0% or both in 3.1%. The median SBP was 150 mmHg (range 80-310), with 18.6% classified as hypertensive (SBP 160-179 mmHg) and 21.1% as severely hypertensive (SBP ⩾180 mmHg). The measured SBP was significantly affected by the cat's demeanor, duration of SBP assessment, presence of CKD and/or hyperthyroidism, the cat's sex and age, and the presence of concomitant therapy. The duration of SBP assessment was significantly affected by the cat's demeanor., Conclusions and Relevance: In veterinary clinics, SBP can be measured in most cats within a short period of time using either Doppler or oscillometric equipment. The presence of CKD or hyperthyroidism was associated with significantly higher SBP values, and anxious or nervous cats had higher SBP values and took longer to obtain SBP assessments.

Objectives: Radioactive iodine ( 131 I) is the preferred treatment for feline hyperthyroidism but neither the optimal 131 I dose nor consistent predictors of post-treatment azotaemia have been determined. The aims of the study were to evaluate the relationships between: (1) 131 I dose and survival; and (2) pretreatment and post-treatment serum creatinine concentration., Methods: Medical records of hyperthyroid cats treated with 131 I at a single referral hospital were reviewed. Information regarding signalment, body weight, pretreatment and post-treatment serum total thyroxine concentration (TT4), serum creatinine concentration, 131 I dose and survival were determined. Multivariable Cox proportional hazards analysis was used to identify variables associated with survival. Multivariable linear regression analysis was used to identify variables associated with post-treatment serum creatinine concentration., Results: One hundred and ninety-eight (79 male, 119 female) cats were treated for hyperthyroidism with 131 I (median dose 138 MBq; interquartile range 92-168). Median survival time was 1153 days (range 16-1871). Post-treatment serum creatinine ( P <0.001) and age ( P  = 0.049) were significantly associated with survival. Every 10 µmol/l increase in post-treatment serum creatinine concentration and every year increase in age was associated with a 1.07-fold (confidence interval [CI] 1.04-1.11) and 1.17-fold (CI 1.00-1.37) increase in the daily hazard of death, respectively. Pretreatment serum creatinine concentration was directly, and post-treatment serum TT4 concentration was inversely, associated with post-treatment serum creatinine concentration. Every 1 μmol/l increase in pretreatment serum creatinine concentration was associated with an increase in post-treatment serum creatinine concentration of 0.7 μmol/l (SE 0.17; P <0.001). Conversely, every 1 nmol/l decrease in post-treatment serum TT4 concentration was associated with a 1.2 μmol/l (SE 0.61; P <0.001) increase in post-treatment serum creatinine concentration., Conclusions and Relevance: Post-treatment serum TT4 concentration was associated with post-treatment azotaemia, which was associated with survival. Although 131 I dose was not directly associated with survival, dosing strategies that minimise post-treatment hypothyroidism and azotaemia could improve patient survival.

Hyperthyroidism and chronic kidney disease (CKD) are common diseases of geriatric cats, and often occur concurrently. Thus, a thorough understanding of the influence of thyroid function on renal function is of significant value for all feline practitioners. Among other effects, hyperthyroidism causes protein catabolism and increases renal blood flow and glomerular filtration rate (GFR). These effects render traditional renal markers insensitive for the detection of CKD in cats with uncontrolled hyperthyroidism. Furthermore, the development of iatrogenic hypothyroidism with over treatment of hyperthyroidism can be detrimental to renal function and may negatively affect long-term survival. This review discusses important diagnostic considerations of feline hyperthyroidism, as well as key treatment modalities, with an emphasis on the use of radioiodine and the importance of post treatment monitoring of thyroid and renal parameters. In Australia, a common curative treatment for cats with benign hyperthyroidism (i.e. thyroid hyperplasia or adenoma) is a fixed dose of orally administered radioiodine, regardless of the serum total thyroxine concentration at the time of diagnosis. This review discusses the long term outcomes of this standard of care in comparison with current, relevant research literature from around the world. Finally, this review explores the use of symmetric dimethylarginine (SDMA) in assessing renal function before and after treatment in hyperthyroid cats. SDMA correlates well with GFR and creatinine in non-hyperthyroid cats, but our understanding of its performance in hyperthyroid cats remains in its infancy., (© 2022 The Authors. Australian Veterinary Journal published by John Wiley & Sons Australia, Ltd on behalf of Australian Veterinary Association.)

Objectives: Although radioiodine ( 131 I) is the treatment of choice for feline hyperthyroidism, 131 I-dosing protocols commonly induce iatrogenic hypothyroidism and expose azotaemia. A recently reported patient-specific 131 I dosing algorithm minimised the risk of 131 I-induced hypothyroidism and azotaemia, while maintaining high cure rates. The aim of the study was to report results of 131 I treatment in a European population of hyperthyroid cats using this patient-specific dosing algorithm., Methods: This prospective case series (before-and-after study) evaluated 165 hyperthyroid cats referred for 131 I treatment. All cats had serum concentrations of thyroxine (T4), triiodothyronine (T3) and thyroid-stimulating hormone (TSH) measured (off methimazole ⩾1 week). Thyroid volume and percentage uptake of 99m Tc-pertechnetate (TcTU) were determined using thyroid scintigraphy. An initial 131 I dose was calculated by averaging dose scores for T4/T3 concentrations, thyroid volume and TcTU; 70% of that composite dose was then administered. Twenty-four hours later, percentage 131 I uptake was measured, and additional 131 I administered as needed to deliver an adequate radiation dose to the thyroid tumour(s). Serum concentrations of T4, TSH and creatinine were determined 6-12 months later., Results: Median calculated 131 I dose was 2.15 mCi (range 1.2-7.5), with only 51 (30.9%) receiving ⩾2.5 mCi. Of 165 cats, 124 (75.2%) became euthyroid, seven (4.2%) became overtly hypothyroid, 27 (16.4%) became subclinically hypothyroid and seven (4.2%) remained hyperthyroid. A higher proportion of overtly (85.7%) and subclinically (26.9%) hypothyroid cats developed azotaemia than euthyroid cats (13.6%; P  = 0.0002). Hypothyroid cats were older ( P  = 0.016) and more likely to have detectable TSH concentrations ( P  = 0.025) and symmetrical bilateral distribution of 99m Tc-pertechnetate uptake ( P  = 0.0002), whereas persistently hyperthyroid cats had higher severity scores ( P  = 0.012)., Conclusions and Relevance: Our results confirm that 131 I dosing with this new algorithm results in high cure rates, with a lowered prevalence of 131 I-induced overt hypothyroidism and azotaemia. Age, serum TSH concentrations, bilateral, symmetrical uptake and severity score help predict outcome.

Practical Relevance: Both hyperthyroidism and chronic kidney disease (CKD) are common long-term conditions in older cats, which might be diagnosed concurrently or develop at different times. Hyperthyroidism may mask the presence of CKD, and vice versa, by various mechanisms that are described in this review. Hyperthyroidism treatment options should be carefully considered when CKD has also been diagnosed., Clinical Challenges: Although it can be difficult to diagnose hyperthyroidism and CKD simultaneously, given that one condition may mask the other, it is important to consider the presence of both diseases when examining an older cat presenting with vomiting, weight loss, polyuria/ polydipsia, anorexia or sarcopenia. The concurrent presence of hyperthyroidism and CKD requires careful monitoring of glomerular filtration rate biomarkers, and adequate and prompt support of kidney function when normal thyroid function is re-established. Iatrogenic hypothyroidism is a recognised complication of all of the treatment options for hyperthyroidism, and increases the risk of azotaemia. Therapy with levothyroxine is recommended for cats that are hypothyroid and azotaemic., Evidence Base: The information in this review draws on current literature and guidelines related to the pathophysiology, diagnosis and treatment recommendations for feline hyperthyroidism and CKD.

Objectives: The aim of this study was to evaluate the efficacy of gabapentin as an anxiolytic in hyperthyroid cats., Methods: Cats (n = 47) with confirmed hyperthyroidism were successfully enrolled. The cat owner allocated a temperament score and a transport stress score at their first visit. For the second visit the cat owner (blinded to treatment) administered either liquid gabapentin 20 mg/kg (n = 22) or an indistinguishable placebo solution (n = 25) 1 h prior to leaving home. A second transport score was allocated by the cat owner at this visit. Upon admission a compliance score was independently assigned by two veterinary nurses blinded to treatment. Excess blood from routine blood draw was analysed for gabapentin plasma concentration from cats in the gabapentin group., Results: There were no significant differences in baseline transport score between groups ( P = 0.13), but significant differences were noted in the second visit transport score between cats medicated with gabapentin compared with placebo ( P = 0.018). Mean compliance scores were significantly different between cats in the treatment group compared with placebo ( P = 0.019). Further sedation was required to complete the procedures in 24% of cats in the placebo group compared to 9% in the gabapentin group ( P = 0.25). Mean plasma gabapentin concentrations were 10.1 mg/l (range 1.7-22.7) in the gabapentin group within a 1-3 h time frame post-administration., Conclusions and Relevance: Hyperthyroid cats medicated with 20 mg/kg gabapentin 1 h prior to leaving home were more relaxed during transport and more compliant with veterinary procedures than cats administered a placebo solution.

Objectives: The objective of this study was to evaluate the presence of traces of thiamazole in the urine of owners of hyperthyroid cats treated with antithyroid drugs., Methods: Urine was collected from 24 owners of hyperthyroid cats, five human patients treated with thiamazole and five healthy humans without any contact with antithyroid drugs. All owners of hyperthyroid cats were asked to fill out a questionnaire. Urine of hyperthyroid cats was collected by spontaneous micturition. All urine samples were stored at -20°C until analysis by ultra-high-performance liquid chromatography coupled to high-resolution quadrupole Orbitrap mass spectrometry., Results: These owners were assessed to have a lot of contact with their cat. Adherence to antithyroid medication handling guidelines was rather poor. High concentrations of thiamazole were detected in all feline samples (median concentration 2818 ng/ml; range 104-15,127) and in the urine of all human patients treated with thiamazole (median concentration 4153 ng/ml; range 1826-5009). No thiamazole was detected in the urine of owners of hyperthyroid cats (limit of detection 3.88 ng/ml; limit of quantification 11.75 ng/ml)., Conclusions and Relevance: The results regarding the potential exposure of owners of hyperthyroid cats to antithyroid drugs are reassuring. Nevertheless, prudence is still warranted when administering antithyroid drugs. Whether these results can be extrapolated to the use of transdermal application requires further investigation.

Hyperthyroidism is a common endocrinopathy of domestic felines. In humans, toxic nodular goitre is pathophysiologically similar to feline hyperthyroidism and can be caused by chronically low or fluctuating dietary iodine intake. The aetiopathogenesis of feline hyperthyroidism is not known, but chronically low or fluctuating dietary iodine intake is likely common. This study assessed habitual iodine intake in domestic cats by: (1) conducting a dietary survey involving 361 owners of 549 cats, (2) analysing iodine content of 119 cat feeds, 38 urine and 64 hair samples and (3) assessing variation in iodine content of eight cat feeds over 4-6 different batches. Owners varied their cats feed regularly, usually on a day-to-day basis and often between wet and dry feeds with differing flavours. The majority (78%; 93 of 119) feeds for cats were within the guideline range for iodine. Of the 22% (n = 26 feeds) that were not compliant, the majority (n = 23) were below the nutritional minimum value with most (n = 16) being dry kibble. Iodine content of feeds did not vary considerably between types of feed or feed packaging, but variation between different batches of the same feed was 14-31%. Hence, urine iodine in cats also varied markedly. Cats being treated for hyperthyroidism had lower hair iodine. In conclusion, a survey assessing how domestic cats are fed, together with an analysis of commercial cat feeds suggests that domestic cats are likely to experience chronically low or fluctuating dietary iodine intake. The latter is supported by wide variation in urine iodine content., (© 2022. The Author(s).)

Objective: This retrospective study was initiated to evaluate the utility of TSH measurements using a common canine TSH assay to diagnose and monitor feline hyperthyroidism after radioiodine or thyreostatic drug treatment., Material and Methods: The electronic database of the University of Veterinary Medicine Vienna was searched for combined TSH and T4 measurements. 217 pairs of TSH and T4 from 136 cats with possible hyperthyroidism were assigned to group A (untreated; n = 24) and B (treated; n = 193). Measurements in group B were then subcategorized according to T4 concentrations (reference range 15-50 nmol/L): group B1 = elevated T4 (n = 46), group B2 = normal T4 (n = 84) and group B3 = decreased T4 (n = 63). Group B2 was further divided into cats with low normal (group B2a; n = 35), medium normal (group B2b; n = 29) and high normal (group B2c; n = 20) T4 concentrations., Results: TSH was detectable in 4 (17 %) of the 24 untreated cats (group A) and did not return to normal despite seemingly successful therapy in two. Increased TSH concentrations were observed in 3.6 % of the treated cats in group B2 and 2.9 %, 6.9 %, and 0 % in subgroups B2a, B2b and B2c, respectively. Forty-four percent of the treated cats with a decreased T4 (group B3) had an increased TSH concentration. TSH correlated with treatment length (r = 0.358, p = 0.004) and was significantly higher in cats treated for more than 3 months (p = 0.008)., Conclusion: TSH was detectable in a significant number of untreated hyperthyroid cats and thus this parameter should not be used to definitively rule out feline hyperthyroidism. Furthermore, the very low prevalence of increased TSH concentrations in treated hyperthyroid cats with a normal T4 and cost benefit calculations do not support the routine measurement of TSH in these cats. The fact that TSH correlated with time since treatment start and 56 % of the cats with a decreased T4 had TSH concentrations within the reference limits, suggests delayed recovery of the pituitary thyrotrophs which might explain the low prevalence of subclinical hypothyroidism in the present study., Clinical Relevance: TSH measurement in cats with suspected or treated hyperthyroidism using a canine assay lacks diagnostic sensitivity and can only complement therapeutic decision-making., Competing Interests: The authors confirm that they do not have any conflict of interest., (Thieme. All rights reserved.)

Objectives: The aim of this study was to investigate the impact of radioiodine treatment (RIT) on the acute phase proteins (APPs) serum amyloid A (SAA), alpha-1-acid glycoprotein (AGP) and haptoglobin (Hp) in hyperthyroid cats., Methods: Between June 2013 and November 2014, 33 hyperthyroid cats without clinical or laboratory signs of inflammatory or neoplastic disease and a body weight >2.5 kg were enrolled. Immediately before, and 12, 36, 72 h and 6 days after RIT, serum samples were obtained for determination of APP concentrations., Results: Both SAA and AGP concentrations changed significantly after RIT. The concentration of AGP increased gradually after treatment with a maximum concentration at the end of the study period (median baseline 398 μg/ml; median 6 days post-RIT 562 μg/ml [ P  = 0.001]). A relevant >two-fold increase in AGP was seen in 8/33 (24%) cats. SAA concentration increased significantly within 12 h (baseline 9.2 μg/ml; 12 h post-RIT 22.5 μg/ml [ P  = 0.012]). In 7/33 (21%) cats, a clinically relevant >10-fold increase in SAA was observed. Hp concentration showed no significant change ( P  = 0.12)., Conclusions and Relevance: RIT induced a mild, mainly not clinically relevant acute phase reaction (APR). AGP and SAA were useful APPs to determine RIT-induced APR.

Background: Hyperthyroidism is the most frequent endocrinopathy in older cats. To date, there is no consensus on how to best calculate the dose of radioiodine to administer to hyperthyroid cats., Aim: The goals of this study were to compare thyroid function, renal function, and survival time between hyperthyroid cats receiving a fixed dose of radioiodine and those receiving an individualized dose calculated using a clinical scoring system., Methods: Medical records of 110 cats treated with radioiodine therapy at the University of Bern between 2010 and 2020 were reviewed. Thyroid function, renal function, and survival of cats treated with a fixed dose of radioiodine (2010-2015; n = 50) were compared to those of cats treated with an individualized dose (2015-2020; n = 60) at different time points after therapy., Results: Treatment with a fixed dose of radioiodine (mean = 168 ± 26 MBq) was associated with 69% of euthyroidism, 19% persistent hyperthyroidism, and 12% hypothyroidism, whereas treatment with an individualized dose (mean = 120 ± 30 MBq) led to 54% euthyroidism, 23% hyperthyroidism, and 23% hypothyroidism ( p = 0.73). More than 12 months after treatment, the incidence of azotemia was comparable between cats treated with a fixed dose (37%) and those treated with an individualized dose (31%) ( p = 0.77). No factors were found to be predictive of treatment failure (hypothyroidism or hyperthyroidism) after therapy. Median survival time after radioiodine therapy was 44 months. In a multivariate analysis, persistent hyperthyroidism was the only variable independently associated with a shorter survival time (HR = 6.24, p = 0.002)., Conclusion: The method of calculating the dose of radioiodine (fixed vs . individualized) to treat feline hyperthyroidism does not appear to be decisive for posttreatment thyroid function, renal function, or survival., Competing Interests: The authors declare that there are no conflicts of interest.

Background: Radioiodine ( 131 I) is the treatment of choice for cats with hyperthyroidism. After 131 I, however, euthyroidism is not always achieved, with 5% to 10% of cats remaining persistently hyperthyroid and 20% to 50% developing iatrogenic hypothyroidism., Objectives: To identify pretreatment factors that may help predict persistent hyperthyroidism and iatrogenic hypothyroidism after treatment of cats using a novel 131 I dosing algorithm., Animals: One thousand and four hundred hyperthyroid cats treated with 131 I., Methods: Prospective, before-and-after study. Pretreatment predictors (clinical, laboratory, scintigraphic, 131 I dose, 131 I uptake measurements) of treatment failure or iatrogenic hypothyroidism were identified by multivariable logistic regression analysis., Results: Cats that developed iatrogenic hypothyroidism were more likely to be older (odds ratio [OR] = 1.10; 95% confidence interval [CI], 1.04-1.17; P = .001), female (OR = 2.04; 95% CI, 1.54-2.70; P < .001), have detectable serum thyroid-stimulating hormone (TSH) concentrations (OR = 4.19; 95% CI, 2.0-8.81; P < .001), have bilateral thyroid nodules (OR = 1.57; 95% CI, 1.19-2.08; P < .001), have homogeneous, bilateral distribution of 99m Tc-pertechnetate uptake (OR = 2.93; 95% CI, 2.05-4.19; P < .001), have milder severity score (OR = 0.62; 95% CI, 0.49-0.79; P < .001), and have higher 131 I uptake (OR = 2.40; 95% CI, 1.75-3.28; P < .001). In contrast, cats remaining persistently hyperthyroid were more likely to be younger (OR = 0.81; 95% CI, 0.72-0.92; P < .001), have higher severity score (OR = 1.87; 95% CI, 1.51-2.31; P < .001), and have lower 131 I uptake (OR = 3.50; 95% CI, 1.8-6.80; P < .001)., Conclusions and Clinical Importance: Age, sex, serum TSH concentration, bilateral and homogeneous 99m Tc-pertechnetate uptake on scintigraphy, severity score, and percent 131 I uptake are all factors that might help predict outcome of 131 I treatment in hyperthyroid cats. Cats with persistent hyperthyroidism had many predictive factors that directly contrasted those of cats that developed 131 I-induced hypothyroidism., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Historical and recent literature disagree on whether a higher PO 131 I dosage, compared to IV or SC routes, is required for successful resolution of spontaneous hyperthyroidism in cats, necessitating investigation into the effect of PO and injectable radioactive iodine administration on % thyroidal radioactive iodine uptake (RAIU)., Hypothesis/objectives: To investigate the effect of PO and SC routes of 123 I administration on paired % thyroidal RAIU in euthyroid cats. Specifically, a 1.5-fold difference (50% relative change) was hypothesized, which in absolute terms can be expressed as a 3.25% increase in the mean %RAIU of 7.04% after PO 123 I administration to 10.56% after SC dosing., Animals: Seven healthy euthyroid teaching-research colony cats., Methods: A randomized, radiologist-blinded crossover study comparing %RAIU after PO and SC 123 I administration., Results: Percentage thyroidal RAIU values (mean ± SD; 95% confidence interval) after PO (4.81% ± 1.63%; 3.30%-6.23%) and SC (5.26% ± 2.43%; 3.01%-7.51%) 123 I administration were associated with a median within-pair absolute difference of 0.2% (range: min, 0.1%-max, 4.9%). Statistical significance was not achieved (P  =  .45). Six of 7 cats had a within-pair absolute difference of 0.1% to 0.9% (relative change of 4%-20%), but a single outlier cat had a within-pair absolute difference of 4.9% (relative change of 108%)., Conclusions and Clinical Importance: This study did not detect an effect of 123 I administration route on paired % thyroidal RAIU in euthyroid cats. However, a type 2 statistical error due to small sample size is possible., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Hyperthyroid cats might have a predisposition to arterial thrombus formation. The mechanism for thrombogenesis currently is unknown but could be associated with systemic hypercoagulability as seen in hyperthyroid humans., Objective: Our purpose was to evaluate markers of hemostasis in hyperthyroid cats compared to healthy cats, and in hyperthyroid cats before and after radioactive iodine treatment (RIT)., Animals: Twenty-five cats with hyperthyroidism and 13 healthy euthyroid cats >8 years of age., Methods: Prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen concentration, antithrombin (AT), D-dimers, thrombin-antithrombin complexes (TAT), von Willebrand Factor antigen (vWF : Ag), and activity of factors VIII and IX were measured. An echocardiogram was performed in all cats. Hemostatic markers and echocardiogram were evaluated again 6 to 9 months after successful RIT in 7 cats., Results: Hyperthyroid cats had higher fibrinogen concentration (P < .0001), AT activity (P < .0001), and vWF : Ag concentration (P = .01) than healthy control cats with all results decreasing significantly post-RIT. Hyperthyroid cats were not more likely to be in a hypercoaguable state than euthyroid cats (P = .08). Serum T4 concentration was not a predictor of a hypercoagulable state (P = .53)., Conclusions and Clinical Importance: Hyperthyroid cats have evidence of altered hemostasis that does not appear to be solely attributable to cardiac abnormalities, but no evidence of a hypercoagulable state. Findings suggest altered hemostasis resolves after RIT. Hyperthyroid cats could have endothelial dysfunction as indicated by increased vWF : Ag which could potentiate thrombogenesis., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objectives: The study aimed to document the incidence of erythrocyte microcytosis in a population of hyperthyroid cats referred for radioiodine (RAI) treatment. Microcytosis has been observed but not described in feline hyperthyroid patients and is associated with hyperthyroidism in humans., Methods: Retrospective clinicopathological data were collected for cats undergoing RAI between January and December 2017. Microcytosis was defined as mean cell volume (MCV) <41.3 fl using the ADVIA 2120 haematology analyser (Siemens) and identified on blood smear examination by a haematology laboratory scientist or board-certified specialist in veterinary clinical pathology. Hyperthyroidism was classified as mild (total thyroxine [TT4] 60-124.9 nmol/l), moderate (TT4 125-250 nmol/l) or severe (TT4 ⩾251 nmol/l) immediately before RAI. Data were analysed descriptively and using a Pearson correlation coefficient to test the relationship between TT4 and microcytosis, and time elapsed between first diagnosis and MCV., Results: There were 41 female and 37 male cats with an age range of 7.2-20.8 years. Most cats were non-pedigree (98.7%). Microcytosis (median MCV 39.8 fl, interquartile range 32.3-41.2) was present in 29.5% (23/78) of the cats. Of the 23 microcytic samples, 86.9% (20/23) were confirmed as such on smear examination. Of mildly, moderately and severely hyperthyroid cats, 23% (6/26), 28.1% (9/32) and 40% (8/20) were microcytic, respectively. Two microcytic cats had low red blood cell counts (<6 × 10 12 /l) and low haemoglobin concentration (<8.2 g/dl). There was no correlation between TT4 or time elapsed from first diagnosis and MCV. Microcytosis resolved in 77.7% (7/9) of cases with follow-up. One microcytic cat had significant comorbidities (portosystemic shunt)., Conclusions and Relevance: Microcytosis was present in a significant proportion of hyperthyroid cats, most without clinically significant comorbidities, and resolved in some following RAI.

Background: Radioiodine ( 131 I) is the treatment of choice for hyperthyroidism in cats, but current 131 I-dosing protocols can induce iatrogenic hypothyroidism and expose azotemia., Objectives: To develop a cat-specific algorithm to calculate the lowest 131 I dose to resolve hyperthyroidism, while minimizing risk of iatrogenic hypothyroidism and subsequent azotemia., Animals: One thousand and four hundred hyperthyroid cats treated with 131 I., Methods: Prospective case series (before-and-after study). All cats had serum concentrations of thyroxine (T 4 ), triiodothyronine (T 3 ), and thyroid-stimulating hormone (TSH) measured (off methimazole ≥1 week). Using thyroid scintigraphy, each cat's thyroid volume and percent uptake of 99m Tc-pertechnatate (TcTU) were determined. An initial 131 I dose was calculated by averaging dose scores for T 4 /T 3 concentrations, thyroid volume, and TcTU; 80% of that composite dose was administered. Twenty-four hours later, percent 131 I uptake was measured, and additional 131 I administered, as needed, to deliver an adequate radiation dose to the thyroid tumor(s). Serum concentrations of T 4 , TSH, and creatinine were determined 6 to 12 months later., Results: The median calculated 131 I dose was 1.9 mCi (range, 1.0-10.6 mCi); 1380 cats required additional 131 I administration on day 2. Of the cats, 1047 (74.8%) became euthyroid, 57 (4.1%) became overtly hypothyroid, 240 (17.1%) became subclinically hypothyroid, and 56 (4%) remained hyperthyroid. More overtly (71.9%) and subclinically (39.6%) hypothyroid cats developed azotemia than euthyroid cats (14.2%; P < .0001)., Conclusions and Clinical Importance: Our algorithm for calculating individual 131 I doses resulted in cure rates similar to historical treatment rates, despite much lower 131 I doses. This algorithm appears to lower prevalence of both 131 I-induced overt hypothyroidism and azotemia., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Radioactive iodine (RAI) is considered the gold standard treatment for feline hyperthyroidism. Currently exposure limits to radiation are regulated by national legislation, therefore the length of the isolation period in hospital for cats receiving radioactive treatment varies according to the place where the radioactive facility is located. The aim of this study was to establish when retained radioactivity decreases in cats receiving subcutaneous I-131 to a level that would allow discharge of cats from the hospital while being compliant with current United Kingdom legislation., Methods: Clinical records of cats treated with subcutaneous I-131 were retrospectively reviewed. Radioactive emission rates were measured using an external probe. Retained radioactivity below 11 MBq at the point of discharge was required by the initial risk assessment to ensure that a 0.3 mSv dose constraint was maintained for owners following standard cat-owner contact restrictions. Average retained activity for each treatment regimen at the time of discharge was calculated. The biological half-life for iodine retention was also calculated., Results: Overall, an end activity below 11 MBq was reached at day 11 in 49% of cats, and at day 13 in 91% of cats. These cats were allowed to be discharged according to UK legislation, as long as contact restrictions were applied at home for 2 weeks., Conclusion: Based on our study, an isolation period of 13 days before allowing discharge of cats treated with subcutaneous RAI (I-131) is compliant with current UK legislation., (© 2021 British Veterinary Association.)

Background: There is limited published information on the outcome for cats where total thyroxine concentration (TT4) remains elevated after treatment with radioactive iodine (RAI)., Objective: To determine the frequency of, and predictors for, subsequent treatment failure in cats for which TT4 remains elevated at hospital discharge, and to report clinical outcomes for cats requiring repeat treatment., Animals: One hundred twenty-one cats with TT4 ≥40 nmol/L after treatment with RAI (out of an original, treated study sample of 959 cats)., Methods: Retrospective study. Data regarding signalment, weight, TT4 concentration (before RAI treatment, at discharge, and percentage change), day of sampling, and I-131 dose were acquired. Logistic regression was performed to evaluate predictors of treatment failure., Results: In the 87 cats for which classification was possible, 35 (40%) became euthyroid without further treatment. All TT4 variables and weight normalized RAI dose were independently predictive of subsequent treatment failure. In multivariate analysis, TT4 concentration at discharge (P < .001) and weight normalized RAI dose (P = .04) remained in the final model. All 28 cats with TT4 concentration ≥150 nmol/L at discharge ultimately failed treatment, compared with 13/40 (32.5%) and 11/19 (57.9%) cats with TT4 concentrations of 40-100 nmol/L and 100-150 nmol/L, respectively. Of the 52 cats that failed treatment, 14 were subsequently managed medically, 12 underwent thyroidectomy (4 with carcinoma), 14 had repeat RAI treatment which was successful in 12/14 (86%) cats, and 13 had no further treatment., Conclusions and Clinical Importance: Cats with TT4 >150 nmol/L at discharge after RAI might be candidates for immediate repeat treatment., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Injectable radioactive iodine (I-131) frequently is used to treat hyperthyroidism in cats. In human medicine, residual activity after injection of radionuclides has been reported, and the actual quantity administered is recorded after administration., Objective: Our aim was to evaluate actual administered dose variability after administration of preprepared I-131 single unit doses for the treatment of hyperthyroidism in cats., Animals: Twenty-seven cats with hyperthyroidism treated with I-131 between April 2017 and March 2019., Methods: Retrospective observational study of cats treated with preprepared single unit I-131 doses. For each dose, the measured activity before administration and residual activity were recorded. The measured dose and the actual dose administered were compared to the prescribed dose., Results: Measured activity before administration ranged from 88.4% to 103.3% of the prescribed dose. Mean residual activity was 5.2 ± 3.0 MBq (ranging from 1.5% to 15% of the prescribed dose). The actual dose administered (measured activity - residual activity) ranged from 79.1% to 100.2% of the prescribed dose. Seventeen of 28 (60.7%) of the actual administered doses differed between 10% and 20% of the prescribed dose. One administered dose had a >20% difference compared to the prescribed dose (79.10% of the prescribed dose)., Conclusion and Clinical Importance: Our study identified variability in the residual and actual administered activity of I-131 as compared to the prescribed dose, which should be taken into consideration when treating cats with (predrawn) I-131., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Background: Liver-type fatty acid-binding protein (L-FABP) and neutrophil gelatinase-associated lipocalin (NGAL) are candidate biomarkers for the detection of early chronic kidney disease (CKD) in cats., Objective: To evaluate urinary and serum L-FABP and NGAL concentrations in CKD cats and in hyperthyroid cats before and after radioiodine ( 131 I) treatment., Animals: Nine CKD cats, 45 healthy cats and hyperthyroid cats at 3 time points including before (T0, n = 49), 1 month (T1, n = 49), and 11 to 29 months after (T2, n = 26) 131 I treatment., Methods: Cross-sectional and longitudinal study. Serum L-FABP (sL-FABP), serum NGAL (sNGAL), urinary L-FABP (uL-FABP), and urinary NGAL (uNGAL) were compared between the 3 groups and between hyperthyroid cats before and after treatment. Data are reported as median (min-max)., Results: CKD cats had significantly higher sL-FABP (13.50 [3.40-75.60] ng/ml) and uL-FABP/Cr (4.90 [0.97-2139.44] µg/g) than healthy cats (4.25 [1.34-23.25] ng/ml; P = .01 and 0.46 [0.18-9.13] µg/g; P < .001, respectively). Hyperthyroid cats at T0 had significantly higher uL-FABP/Cr (0.94 [0.15-896.00] µg/g) than healthy cats (P < .001), thereafter uL-FABP/Cr significantly decreased at T2 (0.54 [0.10-76.41] µg/g, P = .002). For the detection of CKD, uL-FABP/Cr had 100% (95% confidence interval [CI], 66.4-100.0) sensitivity and 93.2% (95% CI, 81.3-98.6) specificity. There were no significant differences in sNGAL and uNGAL/Cr between the 3 groups., Conclusions and Clinical Importance: L-FABP, but not NGAL, is a potential biomarker for the detection of early CKD in cats. Utility of uL-FABP to predict azotemia after treatment in hyperthyroid cats remains unknown., (© 2021 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Objectives: Bisphenol A (BPA) has been mentioned as a possible factor contributing to feline hyperthyroidism. Nevertheless, there are no previous studies reporting on the concentration of BPA in feline serum and its association with thyroid function. The objectives of this study were to measure serum BPA concentration in cats aged ⩾7 years, considered as healthy by their owners, and to compare the results with clinicopathological findings., Methods: Sixty-nine cats aged ⩾7 years considered as healthy by their owners were enrolled in the study. The concentration of BPA in feline serum was measured using liquid chromatography-tandem mass spectrometry. In all cats, signalment, living environment, diet history, and the results of haematological and biochemical analysis, including thyroxine levels, were available., Results: The mean serum BPA concentration in feline serum was 1.06 ± 0.908 ng/ml. Significant correlation was found between BPA concentration and haemoglobin ( r  = 0.3397; P  = 0.0043), haematocrit ( r  = 0.3245; P  = 0.0065) and the number of red blood cells ( r  = 0.2916; P  = 0.0151), concentration of total protein ( r  = 0.2383; P  = 0.0486), concentration of calcium ( r  = 0.3915; P  = 0.0009) and level of bilirubin ( r  = 0.3848; P  = 0.0011). No other significant correlations were found. Significant differences ( P <0.01) were found between mature (1.28 ± 0.994 ng/ml) and geriatric cats (0.420 ± 0.240 ng/ml), between strictly indoor cats (1.27 ± 0.992 ng/ml) and cats with outdoor access (0.660 ± 0.529 ng/ml), and between cats fed canned food (1.23 ± 0.935 ng/ml) and cats fed non-canned food (0.774 ± 0.795 ng/ml)., Conclusions and Relevance: Measurable serum BPA levels were found in all examined samples. The age of the cats was revealed as a significant factor affecting BPA concentration and mature cats had the highest levels. A significantly higher concentration of BPA was found in cats living strictly indoors and in cats fed canned food. No association was found between BPA and thyroid function. Further studies are needed that focus on hyperthyroid cats for better evaluation of this relationship.

Objectives: This study aimed to describe the clinical and diagnostic characteristics, as well as outcomes of radioiodine treatment in dogs with hyperthyroidism caused by a non-resectable ectopic thyroid tumour., Materials and Methods: This retrospective study reviewed the medical records between 2008 and 2018 of dogs diagnosed with hyperthyroidism secondary to a non-resectable ectopic thyroid tumour and treated with radioiodine., Results: Five dogs were included in the study. Three dogs had sublingual ectopic tumours, of which one also had a unilateral cervical thyroid tumour. The remaining two dogs were diagnosed with an ectopic thyroid tumour at the level of the caudal pharynx and the heart base, respectively. All cases were treated with radioiodine. The size of the ectopic masses decreased after radioiodine treatment. Total thyroxine concentrations returned to reference ranges in all dogs. Further, clinical signs of hyperthyroidism disappeared after treatment in all patients. One dog developed myelosuppression secondary to radioiodine treatment. The dog with metastasis had a very short survival compared to the four dogs without metastasis (3 months compared to 7, 36, 50 and 24 months, respectively) and succumbed most likely to thyroid-related problems. In the remaining four dogs, their quality of life improved. They died due to diseases unrelated to the ectopic thyroid tumour., Clinical Significance: Radioiodine therapy should be considered as a treatment option in dogs diagnosed with hyperthyroidism due to a non-resectable ectopic thyroid tumour., (© 2020 British Small Animal Veterinary Association.)

Objectives: Urinary tract infections (UTIs) are reported to be relatively common in hyperthyroid cats, with prevalence rates ranging from 12% to 22%. Factors that are associated with UTIs include age, decreasing body weight and active urine sediments. The purpose of this study was to investigate the prevalence of positive urine cultures (PUCs) in hyperthyroid cats and associated risk factors for PUC., Methods: In total, 197 hyperthyroid cats presenting for radioiodine therapy had urine cultures prospectively performed on cystocentesis samples. Data pertaining to clinical signs, drug history, age, weight, blood urea nitrogen, creatinine, serum thyroxine and urinalysis were also evaluated., Results: The prevalence of PUCs in this population of hyperthyroid cats was 5.1% and all cats were subclinical. Microscopic bacteriuria was significantly associated with a PUC (60%) compared with a negative urine culture (1.6%) status. Age, weight, urine specific gravity <1.020, urine pH, hematuria, pyuria, thyroxine concentration, breed and sex were not associated with PUC status., Conclusions and Relevance: The prevalence of PUCs in this population of cats was lower than previous reports of cats with hyperthyroidism. Cats with a PUC were subclinical at the time of culture, regardless of urine sediment abnormalities. Further studies are necessary to determine the clinical significance of subclinical bacteriuria in hyperthyroid cats.

Objectives: The first objective was to assess correlation between free thyroxine (fT4) measurements by equilibrium dialysis (fT4ED; Antech Diagnostics) and a chemiluminescent enzyme immunoassay (fT4CEIA; IMMULITE 2000 Veterinary Free T4 [Siemens Healthcare Diagnostics Products]) in hyperthyroid, otherwise healthy, cats before (T0), and 1 month (T1) and 11-23 months (T2) after radioactive iodine ( 131 I) therapy. The second objective was to determine correlation between thyroid status based on fT4 (by both techniques) and the gold standard, thyroid scintigraphy., Methods: Thyroid status, including thyroid-stimulating hormone (TSH), total thyroxine (TT4) and fT4 serum concentrations, were assessed in 45 client-owned hyperthyroid cats before (T0), and 1 month (T1) and 11-23 months (T2) after 131 I therapy. fT4 was determined by a chemiluminescent enzyme immunoassay (CEIA) and equilibrium dialysis (ED). Quantitative thyroid scintigraphy (with sodium 99m-Tc-pertechnetate) was performed at T2., Results: Spearman correlation between fT4CEIA and fT4ED was 0.81, 0.88 and 0.79 at T0, T1 and T2, respectively. fT4CEIA was consistently lower than fT4ED, with a median difference of -5.4 pmol/l ( P <0.001) and -4.9 pmol/l ( P <0.0001) at T1 and T2, respectively. At T2, all cats were identified as euthyroid based on thyroid scintigraphy. None of the cats were identified as being hypothyroid, based on serum TT4 and TSH measurements. Nine of 22 (40.9%) cats had an fT4CEIA below the reference interval (RI) at T2, whereas only 2/22 (9.1%) cats had an fT4ED concentration below the RI at T2., Conclusions and Relevance: Good correlation exists between both assays at T1 and T2, but a significant systematic difference is noted at both time points. This could be an indication for reconsideration of the current RI, although further studies are warranted for assessing test accuracy (in otherwise healthy cats and cats with non-thyroidal illness). At this time, routine use of fT4CEIA after 131 I therapy is not advised in feline patients.

Objectives: Cats with hyperthyroidism have been reported to develop thromboembolism, with and without echocardiographic abnormalities consistent with hyperthyroidism. The objective of this study was to compare platelet function in cats with hyperthyroidism with euthyroid age-matched cats. We hypothesized that cats with hyperthyroidism have shortened collagen and adenosine diphosphate (C-ADP) closure times as measured with the platelet function analyzer (PFA-100) in comparison with healthy, age-matched controls., Methods: Sixteen hyperthyroid and nine euthyroid healthy cats >7 years of age were recruited from the hospital population. Platelet function, measured using the C-ADP closure times by the PFA-100, and platelet count were measured in healthy euthyroid cats and cats with hyperthyroidism., Results: Mean ± SD closure times were not significantly different between control (66.3 ± 9.6 s) and hyperthyroid cats (65.9 ± 11.5 s; P  = 0.75). The mean ± SD closure times of hyperthyroid cats that either were untreated or received methimazole for ⩽3 weeks (n = 6; mean 68.5 ± 15.4 s) was not different than that of cats treated for >3 weeks (n = 10; mean 64.3 ± 8.9 s; P  = 0.57). The mean automated platelet count was higher in the hyperthyroid group than in the control group ( P  = 0.023)., Conclusions and Relevance: Platelet function, as measured by closure time under high shear conditions using C-ADP as an agonist, was not affected by hyperthyroidism in this group of cats. Further research is needed to determine if a hypercoagulable state exists in hyperthyroid cats and the potential roles platelets and von Willebrand factor may have.

Hypocobalaminaemia is common in dogs and cats with exocrine pancreatic insufficiency and/or chronic enteropathy. While hypocobalaminaemia has been extensively studied, naturally-occurring serum hypercobalaminaemia (i.e. without supplementation) might be an underestimated finding in small animal medicine. Studies in human medicine have associated hypercobalaminaemia with neoplastic, hepatic and renal disease. Medical records of all dogs and cats with serum cobalamin concentration measurements (2007-2019) were retrospectively analysed; any that had received supplemental cobalamin were excluded from the analysis. Of 654 dogs, 3% (n = 21) were hypercobalaminaemic (median serum cobalamin concentration, 1307 ng/L [965 pmol/L]; range, 914-3561 ng/L [675-2628 pmol/L]). Chronic gastrointestinal signs were common in hypercobalaminaemic dogs (48%). Two of the 21 hypercobalaminaemic dogs were diagnosed with hypoadrenocorticism. Of 323 cats, 11% (n = 34) were hypercobalaminaemic (median serum cobalamin concentration, 1713 ng/L [1264 pmol/L]; range, 1370-3107 ng/L [1011-2293 pmol/L]). The following comorbidities were diagnosed in hypercobalaminaemic cats: chronic enteropathy, 65% (n = 22); acute or chronic pancreatitis, 24% (n = 8); cholangiohepatopathy, 18% (n = 6); gastric lymphoma, 6% (n = 2); and 3% hyperthyroidism (n = 1). Naturally-occurring increased serum cobalamin concentrations occurred infrequently in cats and even less often in dogs. Since hypercobalaminaemia can occur in dogs and cats with severe inflammatory, immune-mediated, and neoplastic conditions, it should not be ignored., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Objectives: To describe the clinicopathological findings and outcomes of cases of feline congenital hypothyroidism diagnosed in a single veterinary hospital in Santiago, Chile., Materials and Methods: Medical records were searched for cases of congenital hypothyroidism over an 18-month period. Inclusion criteria were a diagnosis of congenital hypothyroidism based on consistent historical and clinical findings, a low or low-normal serum total T4 and elevated serum canine TSH (cTSH)., Results: Six unrelated cats ranging in age from 4 to 19 months met the inclusion criteria. The most common historical signs were small stature and lethargy. All cats had disproportionate dwarfism, delayed tooth eruption, retained deciduous teeth, bilateral palpable goitres and low rectal temperatures. Other findings were bradycardia, obesity, poor hair coat and focal alopecia on the ventral aspects of the elbows and hocks. In all cases, cTSH was markedly elevated. Sequential changes noted after the initiation of therapy included normal T4 after 6 weeks, improved hair coat and increased physical activity by 8 weeks, normal cTSH by 10 weeks and normal physical appearance and dentition after 4 months. Goitres shrank markedly but remained palpable. Hypothyroidism was well managed clinically in all cases 2 years after diagnosis except for one cat that died of unrelated causes., Clinical Significance: This is the first report to describe a cluster of congenital hypothyroidism cases in non-related cats that were presented over a short period of time. Growth defects resolve with treatment, even in cats diagnosed after puberty. Larger, prospective multi-centre studies are warranted to determine the incidence of congenital hypothyroidism in cats., (© 2020 British Small Animal Veterinary Association.)

Objectives: Radioiodine (RAI) treatment for hyperthyroidism is becoming increasingly available in the UK. Pretreatment assessment is commonly performed, as patient handling is limited once RAI has been administered. The aims of this study were to determine the prevalence of thoracic pathology using thoracic radiography in hyperthyroid cats referred for RAI treatment and to determine the value of this technique pretreatment., Methods: The hospital databases were searched for hyperthyroid cats referred for RAI treatment at the Feline Centre, Langford Vets, between January 2012 and July 2016. Radiographs were reviewed by Diplomates of the European College of Veterinary Diagnostic Imaging at the time of treatment and each set of radiographs was subsequently reviewed by one radiologist for the study. Cardiorespiratory signs were recorded, if present, and any change in treatment plan or suitability for RAI treatment was documented., Results: Two hundred and fifty-two cats were included in the study. Thoracic pathology was identified in 77% (n = 194/252) of the cats, of which 59% (n = 115/194) had pulmonary abnormalities with bronchial and bronchointerstitial patterns most frequently; 57% (n = 111/194) had skeletal abnormalities and 43% (n = 84/194) had cardiac abnormalities, with mild-to-moderate cardiomegaly most prevalent. Other abnormalities included sternal lymphadenomegaly (7%; n = 13/194), mediastinal pathology (3%; n = 5/194), oesophageal pathology (2%; n = 4/194) and pleural space disease (0.5%; n = 1/194).Twelve cases (6%) had a change in their treatment plan as a result of thoracic radiographic abnormalities, of which five subsequently underwent RAI treatment., Conclusions and Relevance: A low prevalence of significant thoracic pathology was identified on radiographs in hyperthyroid cats referred for RAI treatment. Incidental thoracic abnormalities were found much more commonly; hence, results of thoracic radiology need to be combined with the clinical picture, to decide whether further investigations or alterations to the treatment plan are required pre-RAI.