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The urinary normetanephrine to creatinine ratio (uNMN/Cr) and urinary metanephrine to creatinine ratio (uMN/Cr) are commonly evaluated for the diagnosis of pheochromocytomas (PCC) in dogs. This study aimed to establish reference intervals for uNMN/Cr and uMN/Cr in 56 healthy dogs in Japan and to investigate the effect of urine collection methods on these measurements in 15 non-PCC dogs. The upper limits of reference intervals for uNMN/Cr and uMN/Cr were 124.4 nmol/mmol (90% confidence interval [CI] 107.7-137.0) and 121.1 nmol/mmol (90% CI 102.8-145.1), respectively. Both uNMN/Cr and uMN/Cr were significantly higher when urine was collected in the hospital compared to at home. Several factors, including the method of urine collection, should be considered when utilizing these reference intervals. [ABSTRACT FROM AUTHOR]

Background: Due to the high prevalence of hypertension in patients with autosomal dominant polycystic kidney disease (ADPKD) and advanced chronic kidney disease, diagnosing secondary hypertension poses challenges. We present a rare case of pheochromocytoma in an ADPKD patient to highlight the diagnostic difficulties in identifying secondary hypertension due to pheochromocytoma/paraganglioma (PPGL) in end-stage renal disease (ESRD) patients. Case Report: A 48-year-old female with ADPKD and ESRD experienced recurrent hypertensive crises (up to 220/135 mmHg) accompanied by palpitations and tremors that recurred over the past 2 years. Introduction of a betablocker to the antihypertensive therapy aggravated her symptoms. The initial documentation of elevated urinary metanephrines was interpreted as false positive finding due to renal failure. Subsequent measurements of free plasma metanephrines revealed significant elevations raising suspicion of PPGL. Magnetic resonance imaging identified a 29 mm right adrenal mass. The patient underwent right adrenalectomy resulting in resolution of the hypertensive crises. Discussion: The diagnosis of PPGLs can present significant challenges and is further complicated in ESRD due to nonspecific clinical symptoms and diagnostic pitfalls. Less than 20 PPGL cases have been reported in patients with ESRD. The intolerance of beta-blocker therapy, as well as the use of a scoring system for the likelihood of PPGL should have raised suspicion. Conclusion: PPGL should be considered in all patients with uncontrolled hypertension and beta-blockers intolerance, even in the presence of other etiologic mechanisms such as ESRD. Measuring free plasma metanephrines provides the most reliable biochemical screening in the context of impaired renal function.

Pheochromocytomas and paragangliomas (PPGLs) have emerged as one of the most common endocrine tumors. It epitomizes fascinating crossroads of genetic, metabolic, and endocrine oncology, providing a canvas to explore the molecular intricacies of tumor biology. Predominantly rooted in the aberration of metabolic pathways, particularly the Krebs cycle and related enzymatic functionalities, PPGLs manifest an intriguing metabolic profile, highlighting elevated levels of oncometabolites like succinate and fumarate, and furthering cellular malignancy and genomic instability. This comprehensive review aims to delineate the multifaceted aspects of tumor metabolism in PPGLs, encapsulating genetic factors, oncometabolites, and potential therapeutic avenues, thereby providing a cohesive understanding of metabolic disturbances and their ramifications in tumorigenesis and disease progression. Initial investigations into PPGLs metabolomics unveiled a stark correlation between specific genetic mutations, notably in the succinate dehydrogenase complex (SDHx) genes, and the accumulation of oncometabolites, establishing a pivotal role in epigenetic alterations and hypoxia-inducible pathways. By scrutinizing voluminous metabolic studies and exploiting technologies, novel insights into the metabolic and genetic aspects of PPGLs are perpetually being gathered elucidating complex interactions and molecular machinations. Additionally, the exploration of therapeutic strategies targeting metabolic abnormalities has burgeoned harboring potential for innovative and efficacious treatment modalities. This review encapsulates the profound metabolic complexities of PPGLs, aiming to foster an enriched understanding and pave the way for future investigations and therapeutic innovations in managing these metabolically unique tumors.

Objective: The assessment of primary aldosteronism incorporates adrenal vein sampling (AVS) to lateralize aldosterone excess. Current adrenal vein sampling protocols rely on concurrent cortisol measurements to assess successful cannulation and lateralization and may be inaccurate in the setting of autonomous cortisol secretion. We aimed to compare the measurement of plasma cortisol and metanephrine concentrations to assess cannulation and lateralization during AVS. Design: This is a diagnostic accuracy study in a tertiary referral endocrinology department. Methods: Forty-one consecutive patients with confirmed primary aldosteronism undergoing AVS (49 procedures) were included. None had cortisol autonomy. The use of plasma metanephrine-based ratios were compared with standard cortisol-based ratios to assess cannulation and lateralization during ACTH-stimulated AVS. Results: There was strong agreement between a cortisol selectivity index (SI) ≥5.0 and an adrenal vein (AV) to peripheral vein (PV) plasma metanephrine ratio (AVmet–PVmet) of ≥12.0 to indicate successful cannulation of the AV (n = 117, sensitivity 98%, specificity 89%, positive predictive value (PPV) 95%, negative predictive value (NPV) 94%). There was strong agreement between the standard cortisol-based SI and an AV plasma metanephrine-to-normetanephrine ratio (AVmet–AVnormet) of ≥2.0 to indicate successful cannulation (n = 117, sensitivity 93%, specificity 86%, PPV 94%, NPV 84%). There was strong agreement between the cortisol- or metanephrine-derived lateralization index (LI) > 4.0 for determining lateralization (n = 26, sensitivity 100%, specificity 94.1%, PPV 91.6%, NPV 100%). Conclusions: Ratios incorporating plasma metanephrines provide comparable outcomes to standard cortisol-based measurements for interpretation of AVS. Further studies are required to assess the use of metanephrine-derived ratios in the context of confirmed cortisol autonomy.

Abstract Objective Ketogenic diets like the modified Atkins diet (MAD) are increasingly used in patients with refractory epilepsy. For epilepsy patients, stress is a well‐known seizure‐precipitating factor. New possibilities for measuring biomarkers of stress are now available. The purpose of this study was to investigate the impact of MAD on endocrine stress biomarkers. Methods Forty‐nine patients with drug‐resistant epilepsy were investigated at baseline and after 12 weeks on MAD. Cortisol and cortisol‐binding globulin (CBG) were measured and free cortisol index (FCI) calculated. We also measured metanephrine, normetanephrine, and methoxytyramine, all markers of epinephrine, norepinephrine, and dopamine, respectively. Changes were analyzed according to sex and antiseizure medications. The different markers at baseline and after 12 weeks of MAD treatment were correlated with seizure frequency and weight loss, respectively. Results The change in total cortisol was modest after 12 weeks on the diet (from 432.9 nmol/L (403.1–462.7)) to 422.6 nmol/L (384.6–461.0), P = 0.6). FCI was reduced (from 0.39 (0.36–0.42) to 0.34 (0.31–0.36), P = 0.001). CBG increased during the study (from 1126.4 nmol/L (1074.5–1178.3) to 1272.5 nmol/L (1206.3–1338.7), P

Measurements of plasma metanephrines and methoxytyramine provide a sensitive test for diagnosis of pheochromocytoma/paraganglioma. False-positive results remain a problem, particularly in patients taking norepinephrine reuptake-blocking drugs. Therefore, in this retrospective observational study, we measured plasma metanephrines and methoxytyramine in 61 patients taking norepinephrine reuptake blockers (tricyclic antidepressants or serotonin-norepinephrine reuptake inhibitors) and 17 others taking selective serotonin reuptake inhibitors, all without pheochromocytoma/paraganglioma. We highlight a singular case with strongly elevated plasma normetanephrine and methoxytyramine concentrations associated with norepinephrine reuptake blockade. Data were compared to results from 252 and 1804 respective patients with and without tumors. Plasma normetanephrine was 40% higher (P < 0.0001) in patients on norepinephrine reuptake blockers and methoxytyramine was 127% higher (P = 0.0062) in patients taking tricyclic antidepressants compared to patients not taking uptake blockers and without tumors. The corresponding false-positive rates rose (P < 0.0001) from 4.8% to 23.0% for normetanephrine and from 0.9% to 28.6% for methoxytyramine. Selective serotonin reuptake inhibitors did not increase plasma concentrations of metabolites. In the highlighted case, plasma normetanephrine and methoxytyramine were elevated more than six times above upper reference limits. A pheochromocytoma/paraganglioma, however, was excluded by functional imaging. All biochemical test results normalized after discontinuation of norepinephrine reuptake blockers. These findings clarify that norepinephrine reuptake blockers usually result in mild elevations of normetanephrine and methoxytyramine that, nevertheless, significantly increase the number of false-positive results. There can, however, be exceptions where increases in normetanephrine and methoxytyramine reach pathological levels. Such exceptions may reflect failure of centrally mediated sympathoinhibition that normally occurs with the norepinephrine reuptake blockade. [ABSTRACT FROM AUTHOR]

Context Pheochromocytomas are increasingly diagnosed in incidentally detected adrenal masses. However, the characteristics of incidental pheochromocytomas are unclear. Objective We aimed to assess the proportion and clinical, biochemical, radiological, genetic, histopathological, and follow-up characteristics of incidental pheochromocytomas. Methods A retrospective review was conducted of patients with pheochromocytoma seen between January 2010 and October 2022 at a large UK tertiary care center. The diagnosis was confirmed histologically or by the combined presence of increased plasma and/or urinary metanephrines (MN), indeterminate adrenal mass on cross-sectional imaging, and metaiodobenzylguanidine avidity. Results We identified 167 patients with pheochromocytoma; 144 (86.2%) underwent adrenalectomy, for 23 (13.8%) surgery was either awaited, deemed unsuitable due to frailty or other metastatic malignancy, or declined by the patients. Excluding pheochromocytomas diagnosed via screening genetically predisposed individuals (N = 20), 37 of 132 (28.0%) presented with adrenergic symptoms and/or uncontrolled hypertension, while 91 of 132 (69.0%) patients presented with an incidentally detected adrenal mass. Incidentally detected patients were older (median age 62 years) than those detected due to clinical suspicion (aged 42 years) or after genetic screening (aged 33 years) (all P <.05). Incidentally detected pheochromocytomas were smaller (median 42 mm) than tumors detected due to adrenergic symptoms/uncontrolled hypertension (60 mm), but larger than tumors identified by genetic screening (30 mm) (all P <.05). Increased MN excretion showed a similar pattern (symptomatic/uncontrolled hypertension > incidental > genetic screening) (all P <.05). Hereditary predisposition was detected in 20.4% of patients (incidental, 15.3%; symptomatic/uncontrolled hypertension, 42.9%). Conclusion The majority of pheochromocytomas are diagnosed incidentally and have distinct clinical, radiological, biochemical, and genetic features. Their detection at older age but smaller size may point to a different underlying tumor biology. [ABSTRACT FROM AUTHOR]

Objective: Ketogenic diets like the modified Atkins diet (MAD) are increasingly used in patients with refractory epilepsy. For epilepsy patients, stress is a well‐known seizure‐precipitating factor. New possibilities for measuring biomarkers of stress are now available. The purpose of this study was to investigate the impact of MAD on endocrine stress biomarkers. Methods: Forty‐nine patients with drug‐resistant epilepsy were investigated at baseline and after 12 weeks on MAD. Cortisol and cortisol‐binding globulin (CBG) were measured and free cortisol index (FCI) calculated. We also measured metanephrine, normetanephrine, and methoxytyramine, all markers of epinephrine, norepinephrine, and dopamine, respectively. Changes were analyzed according to sex and antiseizure medications. The different markers at baseline and after 12 weeks of MAD treatment were correlated with seizure frequency and weight loss, respectively. Results: The change in total cortisol was modest after 12 weeks on the diet (from 432.9 nmol/L (403.1–462.7)) to 422.6 nmol/L (384.6–461.0), P = 0.6). FCI was reduced (from 0.39 (0.36–0.42) to 0.34 (0.31–0.36), P = 0.001). CBG increased during the study (from 1126.4 nmol/L (1074.5–1178.3) to 1272.5 nmol/L (1206.3–1338.7), P < 0.001). There were no changes in the metanephrines after 12 weeks on the diet. The decrease in FCI was significant only in women, and only observed in patients using nonenzyme‐inducing ASMs. We did not find any correlation between cortisol, CBG, or FCI levels and seizure frequency. Significance: After being on MAD for 12 weeks, FCI decreased significantly. The reduction in FCI may reflect reduced stress, but it may also be an effect of increased CBG. The reasons behind these alterations are unknown. Possibly, the changes may be a result of a reduction in insulin resistance and thyroid hormone levels. Treatment with MAD does not seem to influence "fight or flight" hormones. [ABSTRACT FROM AUTHOR]

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances. [ABSTRACT FROM AUTHOR]

Phaeochromocytomas (PC) and sympathetic paragangliomas (PGL) are potentially malignant tumours arising from the adrenal medulla (PC) or elsewhere in the sympathetic nervous system (PGL). These tumours usually secrete catecholamines and are associated with significant morbidity and mortality, so accurate and timely diagnosis is essential. The initial diagnosis of phaeochromocytoma/paraganglioma (PPGL) is often dependent on biochemical testing. There is a range of pre-analytical, analytical and post-analytical factors influencing the analytical and diagnostic performance of biochemical tests for PPGL. Pre-analytical factors include patient preparation, sample handling and choice of test. Analytical factors include choice of methodology and the potential for analytical interference from medications and other compounds. Important factors in the post-analytical phase include provision of appropriate reference ranges, an understanding of the potential effects of various medications on metanephrine concentrations in urine and plasma and a consideration of PPGL prevalence in the patient population being tested. This article reviews these pre-analytical, analytical and post-analytical factors that must be understood in order to provide effective laboratory services for biochemical testing in the diagnosis of PPGL. [ABSTRACT FROM AUTHOR]

Background: Adrenal tumors, including benign cortical adenoma (BCA) and pheochromocytoma (PCC) or paraganglioma (PGL), have been more frequently detected during imaging examinations in recent years. However, the associated clinical or laboratory characteristics, especially on the Chinese population, still need to be investigated. Methods: We conducted a retrospective analysis of 491 patients pathologically diagnosed with adrenal tumors, from Jan 19, 2018 to Dec 17, 2019, at a tertiary referral hospital in Wuhan of China. Our findings including 247 (50.3%) BCA cases, and 92 (18.7) PCC/PGL cases and other cases. Both the clinical and laboratory parameters were reviewed and analyzed. Results: Compared with other adrenal tumors, PCC/PGL showed larger tumor diameters and more frequently located on the right side, and were with higher levels of urinary catecholoamines and plasma metanephrines, especially for the 24 h urinary vanilmandelic acid (VMA) and plasma normetanephrine (NMN). The optimal diagnostic thresholds were 29.40 ug/24 h for VMA (sensitivity, 85%; specificity, 91%) and 0.63 nmol/L for NMN (sensitivity, 91%; specificity, 92%). The 24 h urinary VMA and plasma NMN also shared abilities to differentiate between different tumor laterality and different tumor size in PCC/PGL cases. In addition, compared with the other benign tumors, BCA were smaller in diameters (20 vs 35 mm, p < 0.001), and seemed to be lower in levels of plasma epinephrine, dopamine and serum ACTH. Conclusion: 24 h Urinary catecholoamines and plasma metanephrines, especially for the 24 h urinary VMA and plasma MNM, showed higher diagnostic efficacies for PCC/PGL, and were tightly associated with the tumor laterality and tumor size. [ABSTRACT FROM AUTHOR]

Objective. Pheochromocytomas (PHEO) and paraganglioma (PGLs) are rare neuroendocrine catecholamine-producing tumors that arise from the chromaffin cells of either the adrenal medulla or extra-adrenal paraganglionic tissues. Despite the recent advances in imaging technologies, biochemical evidence of excessive catecholamine production by the tumor is considered the most important test for the diagnosis of these tumors. The aim of the present study is to investigate the role of the catecholamine metabolites (normetanephrine and metanephrine) levels in the diagnosis of PHEO/PGLs and to evaluate if their levels correlate with the size of these tumors.

Purpose: Residual adrenocortical function, RAF, has recently been demonstrated in one-third of patients with autoimmune Addison's disease (AAD). Here, we set out to explore any influence of RAF on the levels of plasma metanephrines and any changes following stimulation with cosyntropin. Methods: We included 50 patients with verified RAF and 20 patients without RAF who served as controls upon cosyntropin stimulation testing. The patients had abstained from glucocorticoid and fludrocortisone replacement > 18 and 24 h, respectively, prior to morning blood sampling. The samples were obtained before and 30 and 60 min after cosyntropin stimulation and analyzed for serum cortisol, plasma metanephrine (MN), and normetanephrine (NMN) by liquid-chromatography tandem-mass pectrometry (LC-MS/MS). Results: Among the 70 patients with AAD, MN was detectable in 33%, 25%, and 26% at baseline, 30 min, and 60 min after cosyntropin stimulation, respectively. Patients with RAF were more likely to have detectable MN at baseline (p = 0.035) and at the time of 60 min (p = 0.048) compared to patients without RAF. There was a positive correlation between detectable MN and the level of cortisol at all time points (p = 0.02, p = 0.04, p < 0.001). No difference was noted for NMN levels, which remained within the normal reference ranges. Conclusion: Even very small amounts of endogenous cortisol production affect MN levels in patients with AAD. [ABSTRACT FROM AUTHOR]

Pheochromocytomas are rare catecholamine-secreting neuroendocrine tumors of the adrenal medulla chromaffin cells, usually associated with features of catecholamine excess. Clinically and biochemically silent pheochromocytoma without adrenergic symptoms or elevated catecholamine concentrations are rare. A 71-year-old female presented with acute right flank pain with abdominal computed tomography (CT) scan revealing a hemorrhagic right adrenal mass. She had no preceding adrenergic symptoms, and normal serum electrolytes, on a background of well-controlled hypertension on amlodipine monotherapy. After conservative management and discharge, an outpatient CT adrenal scan confirmed an 88 × 64 mm right adrenal mass demonstrating intense avidity (maximum standardized uptake value, 20.2) on fluorodeoxyglucose F 18-positron emission tomography (FDG-PET)/CT scan. Biochemical screening supported a nonfunctional adrenal lesion with normal-range plasma normetanephrines and metanephrines. She underwent a right adrenalectomy for presumed nonfunctioning adrenocortical cancer; however, histopathology demonstrated a 120-mm pheochromocytoma. Succinate dehydrogenase subunit B (SDHB) and fumarate hydratase (FH) staining were retained; however, weakly positive 2SC staining raised concerns for FH-deficient pheochromocytoma. Germline DNA sequencing was negative for pathogenic RET, VHL, SDHB, SDHD, or FH variants. Tumor cells stained positive for tyrosine hydroxylase and negative for dopamine β hydroxylase. Four months postoperatively, progress FDG-PET/CT scan demonstrated no focal avidity. Massive biochemically silent pheochromocytomas are exceedingly rare, and we discuss various mechanisms that may predispose patients to this phenomenon. [ABSTRACT FROM AUTHOR]

Background: The use of supine reference intervals instead of the corresponding seated reference intervals for seated plasma-free metanephrines (MNs) in pheochromocytoma/paraganglioma (PPGL) screening has been controversial in recent years. Each clinical laboratory should choose the optimal sampling posture and diagnostic strategy according to local conditions. Methods: The reference population consisted of 736 cases aged 14–92 years old and the validation population consisted of 1068 patients aged 8–87 years old. Seated MNs were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the reference intervals and diagnostic cut-off values were established and the diagnostic performance compared with reference intervals established in a supine position. Results: There was no correlation between seated plasma MNs and age (p > 0.05) and there were differences in MNs among the various disease groups (p < 0.05). MNs were different in gender (p < 0.0001). The upper reference limit (URL) established in this study had the same sensitivity (100%) and better specificity (94.6% vs 83.5%) compared with the published age-adjusted supine reference intervals. The proportion of suspected patients with MNs within the URL-2×URL range was lower using seated reference intervals compared to supine intervals (5.3% vs 15.7%). Conclusion: Using the corresponding seated reference intervals for seated plasma MNs can reduce the unnecessary re-examinations of suspected patients with slightly elevated MNs. The cut-off value established by seated plasma MNs has good diagnostic performance in PPGL. Use of seated sampling is an acceptable practice and is more convenient and economical than supine sampling. [ABSTRACT FROM AUTHOR]

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A reliable and robust liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed in this study for clinical testing of 24-h urinary fractionated metanephrines (MNs) and 3-methoxytyramine. At first, the acid hydrolysis condition was well optimized. Following solid-phase extraction (SPE) was performed to purify urine specimens, and the obtained elutes were directly used for LC–MS/MS analysis. A total run time of 3 min for each sample made it possible to analyze more than 300 samples per day. This method was validated with good linearity (linear correlation coefficient ≥ 0.9969), favorable precision (the coefficients of variation ≤ 10.2%), satisfactory recovery (85.0%–108%) and negligible matrix effect (92.0%–109%). The reference intervals of these analytes in Chinese subjects were established for clinical application in diagnosis of pheochromocytoma. This reliable and well-validated measurement method for 24-h urinary fractionated MNs and 3-methoxytyramine using LC–MS/MS could be successful used in clinical testing for diagnosis of pheochromocytoma. [ABSTRACT FROM AUTHOR]

Background. Pheochromocytoma (PH) is a neuroendocrine tumor with a rare incidence in children, that can have high-risk cardiovascular effects. The symptomatology can be absent, or it can start through paroxysmal hypertension associated with headache, sweating, palpitation and dizziness due to catecholamine secretion. Methodology. We report the case of an 8-year-old patient hospitalized in the “Sf. Maria” Emergency Clinical Hospital for Children, Iaşi, Romania, for headache, sweating and palpitation, with progressive deterioration of the general condition, when blood pressure levels remained high despite antihypertensive medication. Results. After identifying the increased levels of urine and plasma metanephrines, the ultrasound and abdominal CT revealed a tumor, and the diagnosis of bilateral pheochromocytoma and secondary arterial hypertension was established. The pheochromocytoma was histopathologically confirmed intraoperatively. The surgical treatment consisted in the subtotal resection of the tumor, with a favorable postoperative and subsequent evolution. Conclusions. A high index of suspicion of pheochromocytoma should be raised if the main causes of hypertension in children were excluded. The surgical treatment is the gold standard, leading to a normalization of blood pressure values. [ABSTRACT FROM AUTHOR]

Purpose: The co-occurrence of cyanotic congenital heart disease (CCHD) and PHEO/PGL has been reported, but the role of the hypoxic environment in the pathogenesis of PHEO/PGL remains unclear. Our aim was to compare plasma metanephrine and normetanephrine levels between patients with CCHD and patients with acyanotic congenital heart disease (ACCHD). Methods: We performed a cross-sectional study in a prospective cohort of 44 patients with congenital heart disease (CHD) (31 (70.5%) females) with a median age of 37.5 (31.0–55.6) years at the time of evaluation. Thirty-two (73%) patients had CCHD and 12 (27%) patients had ACCHD. Morning blood samples for plasma determination of metanephrine and normetanephrine were collected. Results: Plasma normetanephrine levels were significantly higher in patients with CCHD compared to ACCHD (p = 0.002). Ten (31.3%) patients with CCHD had plasma normetanephrine levels elevated above the reference range, while all ACCHD patients had normal levels. Patients with lower oxygen saturation and higher proBNP had significantly higher normetanephrine levels (ρ = −0.444, p = 0.003 and ρ = 0.449, p = 0.002, respectively). No chromaffin cell tumors were detected. Conclusion: Increased plasma normetanephrine levels in patients with CCHD can be explained by the effect of hypoxia. Future research is needed to better understand the impact of chronic hypoxia in CCHD on increased sympathetic outflow, hyperplastic response of chromaffin tissue, and the role of somatic mutations in CCHD-PHEO/PGL pathogenesis related to hypoxia. [ABSTRACT FROM AUTHOR]

Purpose: Pheochromocytomas are rare tumors and biochemically silent ones with normal catecholamine levels are even rarer. Up to date, biochemically inactive pheochromocytomas are poorly investigated. We aimed to systematically assess the pre- and peri-operative characteristics and the outcomes of patients with these tumors who had been treated and followed-up in 2 tertiary centers. Methods: Clinical, laboratory and imaging data, treatment outcomes and follow-up of biochemically silent pheochromocytoma patients were recorded. Results: Ten patients (5 men) [median age at diagnosis 52.5 years (24–72)] were included. Adrenal masses were incidentally discovered in all patients except from one who presented with pheochromocytoma-related manifestations. Twenty-four-hour urine metanephrine and normetanephrine levels were in the low-normal, normal and high-normal range in 4, 4 and 2 patients and in 1, 6 and 3 patients, respectively. Tumors were unilateral [median size 46 mm (17–125)] and high density on pre-contrast CT imaging or high signal intensity on T2-weighted MRI scans were found in all cases. Pre-operatively, 5 patients were treated with phenoxybenzamine [median total daily dose 70 mg (20–100)]. Intra-operatively, 4 patients developed hypertension requiring vasodilator administration and 8 developed hypotension; vasoconstrictors were required in 5 cases. One patient, not pre-operatively treated with phenoxybenzamine, developed Takotsubo cardiomyopathy. During a median 24-month (12–88) follow-up period, one patient had disease progression. Conclusions: The majority (90%) of patients with biochemically silent pheochromocytomas developed hemodynamic instability during adrenal surgery. In patients with biochemically silent adrenal lesions and a high suspicion index for pheochromocytoma based on tumor imaging characteristics, pre-operative alpha-blockade treatment may be advisable. [ABSTRACT FROM AUTHOR]

Phaeochromocytomas (PC) and sympathetic paragangliomas (PGL) are potentially malignant tumours arising from the adrenal medulla (PC) or elsewhere in the sympathetic nervous system (PGL). These tumours usually secrete catecholamines and are associated with significant morbidity and mortality, so accurate and timely diagnosis is essential. The initial diagnosis of phaeochromocytoma/paraganglioma (PPGL) is often dependent on biochemical testing. There is a range of pre-analytical, analytical and post-analytical factors influencing the analytical and diagnostic performance of biochemical tests for PPGL. Pre-analytical factors include patient preparation, sample handling and choice of test. Analytical factors include choice of methodology and the potential for analytical interference from medications and other compounds. Important factors in the post-analytical phase include provision of appropriate reference ranges, an understanding of the potential effects of various medications on metanephrine concentrations in urine and plasma and a consideration of PPGL prevalence in the patient population being tested. This article reviews these pre-analytical, analytical and post-analytical factors that must be understood in order to provide effective laboratory services for biochemical testing in the diagnosis of PPGL.

Pheochromocytoma is a rare neuroendocrine tumour that develops from chromaffin cells in the adrenal medulla and is characterised by the excessive production of catecholamines and their metabolites. Diagnostic confirmation is performed by detecting elevated levels of catecholamines and/or their metabolites in plasma or 24-h urine. In the case of moderate elevations of normetanephrine, the clonidine suppression test may be useful to differentiate between endogenous hypersecretion and false positive results. Once the biochemical diagnosis is performed, the tumour localisation is carried out using imaging techniques and sometimes with nuclear medicine imaging tests. Furthermore, in all patients with pheochromocytomas it is recommended to perform a genetic study to identify hereditary disorders that may be present in more than 30% of cases and to perform a cardiological evaluation to rule out the presence of cardiovascular involvement secondary to the catecholamine hypersecretion., (Copyright © 2024. Publicado por Elsevier España, S.L.U.)

Background: Catecholamines (epinephrine; norepinephrine; and dopamine) and their O-methylated metabolites (metanephrine; normetanephrine; and 3-methoxytyramine) are biomarkers for pheochromocytoma and paraganglioma. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was recommended by Endocrine Society for detecting these compounds. The influence of blood collection tubes on the analysis of the six analytes by LC-MS/MS was not thoroughly investigated, which we want to clarify in our study., Methods: Blood samples of healthy individuals were collected into serum, lithium heparin, and K 2 EDTA plasma tubes separately. Samples were subjected to solid phase extraction and then analyzed by LC-MS/MS. The retention behavior and assay performance of the six analytes were assessed for samples from different collection containers. The impacts of potassium and sodium as the counter ions of EDTA on the retention time and matrix effect were also studied., Results: Compared with O-methylated metabolites, the results for catecholamines were more affected by the collection tubes, especially for norepinephrine, which displayed severely suppressed signal and very low extraction efficiency in K 2 EDTA plasma. Changing the counter ion of EDTA from potassium to sodium dramatically changed the retention behavior and matrix effect of norepinephrine., Conclusions: It is necessary to evaluate blood collection tubes for catecholamines and their O-methylated metabolites analyzed by LC-MS/MS. In addition, attention should also be paid when the anticoagulant counter ion was changed., (© 2024 The Author(s). Journal of Clinical Laboratory Analysis published by Wiley Periodicals LLC.)

The urinary normetanephrine to creatinine ratio (uNMN/Cr) and urinary metanephrine to creatinine ratio (uMN/Cr) are commonly evaluated for the diagnosis of pheochromocytomas (PCC) in dogs. This study aimed to establish reference intervals for uNMN/Cr and uMN/Cr in 56 healthy dogs in Japan and to investigate the effect of urine collection methods on these measurements in 15 non-PCC dogs. The upper limits of reference intervals for uNMN/Cr and uMN/Cr were 124.4 nmol/mmol (90% confidence interval [CI] 107.7-137.0) and 121.1 nmol/mmol (90% CI 102.8-145.1), respectively. Both uNMN/Cr and uMN/Cr were significantly higher when urine was collected in the hospital compared to at home. Several factors, including the method of urine collection, should be considered when utilizing these reference intervals.

Pheochromocytomas are rare neuroendocrine tumors that derive from the chromaffin cells of the adrenal medulla and secrete catecholamines. The measurement of plasma or fractionated urine metanephrines is the hormonal determination of choice for the biochemical diagnosis. Once the biochemical diagnosis is confirmed, the next step is the localization study. It is recommended to request a genetic study in all patients with pheochromocytomas since 40% of cases are hereditary. Once the diagnostic study is completed, preoperative treatment with alpha blockers should be instituted at least 7-14 days before adrenalectomy. However, in low-risk patients, the omission of presurgical treatment could be considered if the surgery is performed in centers with experience and a strict monitoring of the patient is carried out during the perioperative period. This document offers a practical guide on the diagnosis and perioperative approach in patients with pheochromocytomas., (Copyright © 2024 Elsevier España, S.L.U. All rights reserved.)

Von Hippel-Lindau disease (vHL) is a hereditary, autosomal dominant syndrome manifested by a predisposition to the occurrence of benign and malignant neoplasms. The spectrum of vHL-related neoplasms includes: pheochromocytoma (PHEO), central nervous system and retinal hemangioblastomas, renal clear cell carcinoma, epididymal cystadenomas, pancreatic neuroendocrine tumors as well as visceral (renal and pancreatic) cysts. We report the family (5 patients) with genetically confirmed vHL in which every member had PHEO diagnosed during pediatric care. The presented family had a missense variant in the VHL gene (ex1 g.A451G gene, p. S80G) which is connected with an increased risk of PHEO. Performing screening laboratory and imaging tests in patients with genetically confirmed vHL disease can help to avoid the occurrence of disease symptoms and to perform an elective surgery in safe conditions. Due to the risk of coexisting pathologies and the complexity of the disease, patients with vHL require long-term care.

The overproduction of catecholamines in pheochromocytoma/paraganglioma (PPGL) induces a hypermetabolic state. The aim of this study was to evaluate the incidence of a hypermetabolic state and differences in substrate metabolism in consecutive PPGL patients divided by catecholamine phenotype. Resting energy expenditure (REE) and respiratory quotient (RQ) were measured in 108 consecutive PPGL patients and 70 controls by indirect calorimetry. Hypermetabolic state was defined according to the Mifflin St. Jeor Equation as a ratio above 110%. Hypermetabolic state was confirmed in 70% of PPGL patients, regardless of phenotype. Older age, prevalence of diabetes mellitus and arterial hypertension were correlated with hypermetabolic PPGL as compared to normometabolic form. Analysis according to overproduced catecholamine showed differences in VCO2 (p < 0.05) and RQ (p < 0.01) and thus different substate metabolism between phenotypes in hypermetabolic form of PPGL. Lipid utilization was higher in the adrenergic phenotype (p = 0.001) and positively associated with the percentage of REE ratio (R = 0.48, p < 0.001), whereas the noradrenergic phenotype preferentially oxidizes carbohydrates (P = 0.001) and is correlated with the percentage of REE ratio (R = 0.60, p < 0.001). Hypermetabolic state in PPGL is a common finding in both catecholamine phenotypes. Hypermetabolic PPGL patients are older and suffer more from diabetes mellitus and arterial hypertension. Under basal conditions, the noradrenergic type preferentially metabolizes carbohydrates, whereas the adrenergic phenotype preferentially metabolizes lipids. [ABSTRACT FROM AUTHOR]

Les catécholamines (adrénaline et noradrénaline) sont des hormones régulant la pression artérielle et des neuromédiateurs du système nerveux autonome sympathique. Elles sont sécrétées en excès par les tumeurs chromaffines de la médullosurrénale (phéochromocytomes) ou de ganglions sympathiques (paragangliomes). Les catécholamines ainsi que leurs métabolites (dérivés méthoxylés, acide vanillylmandélique et acide homovanillique) et la dopamine sont dosés dans le plasma et les urines par des méthodes basées sur leur séparation par chromatographie liquide haute performance (CLHP) et de plus en plus détectées par spectrométrie de masse en tandem (MS/MS). Les conditions pré-analytiques sont strictes étant donné que l'on ne doit pas stimuler la sécrétion des catécho- lamines. Les recommandations actuelles demandent de doser en premier lieu les dérivés méthoxylés (ou métanéphrines) totaux plasmatiques ou urinaires, alors que la CLHP-MS/MS est capable de doser séparément les formes libres plasmatiques et urinaires. La chromogranine A permet un criblage plus aisé mais n'est encore guère disponible. Le diagnostic positif et le suivi thérapeutique de ces tumeurs parfois cancéreuses nécessitent tout l'arsenal analytique allant des dérivés méthoxylés aux catécholamines elles-mêmes. Catecholamines (epinephrine and norepinephrine) are hormones that regulate arterial pressure and are neurotransmitters of sympathetic autonomous nervous system. They are secreted in excess by chromaffin tumors of adrenal medulla (phaeochromocytoma) or sympathetic lymph nodes (paraganglioma). The catecholamines as well as their metabolites (metanephrines, vanillylmandelic acid and homovanillic acid), and also dopamine, are measured in both plasma and urines by assays based on separation by high performance liquid chromatography (HPLC) and often identified by tandem mass spectrometry (MS/MS). Pre-analytic conditions are difficult because they should not stimulate secretion of catecholamines. Actual recommendations request first measurement of total metanephrines in urines although HPLC-MS/MS can measure separately free forms in both plasma and urines. Chromogranin A allows easily screening, but not yet available. Positive diagnosis and therapeutic nursing of these tumors need the all analytical arsenal from metanephrines to catecholamines their-self. [ABSTRACT FROM AUTHOR]

Catecholamine-producing tumors of childhood include most notably neuroblastoma, but also pheochromocytoma and paraganglioma (PPGL). Diagnosis of the former depends largely on biopsy-dependent histopathology, but this is contraindicated in PPGL where diagnosis depends crucially on biochemical tests of catecholamine excess. Such tests retain some importance in neuroblastoma though continue to largely rely on measurements of homovanillic acid (HVA) and vanillylmandelic acid (VMA), which are no longer recommended for PPGL. For PPGL, urinary or plasma metanephrines are the recommended most accurate tests. Addition of methoxytyramine to the plasma panel is particularly useful to identify dopamine-producing tumors and combined with normetanephrine also shows superior diagnostic performance over HVA and VMA for neuroblastoma. While use of metanephrines and methoxytyramine for diagnosis of PPGL in adults is established, there are numerous pitfalls for use of these tests in children. The establishment of pediatric reference intervals is particularly difficult and complicated by dynamic changes in metabolites during childhood, especially in infants for both plasma and urinary measurements, and extending to adolescence for urinary measurements. Interpretation of test results is further complicated in children by difficulties in following recommended preanalytical precautions. Due to this, the slow growing nature of PPGL and neglected consideration of the tumors in childhood the true pediatric prevalence of PPGL is likely underappreciated. Earlier identification of disease, as facilitated by surveillance programs, may uncover the true prevalence and improve therapeutic outcomes of childhood PPGL. For neuroblastoma there remain considerable obstacles in moving from entrenched to more accurate tests of catecholamine excess.

Objectives. Pheochromocytoma (PCC) is a neuroendocrine tumor derived from chromaffin tissue more frequently found in the adrenal medulla. Many discoveries over the last decade have significantly improved our understanding of PCC.

Background: Phaeochromocytomas and paragangliomas (PPGL) are catecholamine secreting tumours associated with significant morbidity and mortality. Timely diagnosis and management are essential. A range of laboratory tests can be utilised in the investigation of PPGL. There is scope for significant variation in practice between centres. We aimed to investigate how the laboratory investigation of PPGL is performed in laboratories across the United Kingdom. Methods: A questionnaire consisting of 21 questions was circulated to Clinical Biochemistry laboratories in the United Kingdom via the Association for Clinical Biochemistry and Laboratory Medicine office. The survey was designed to allow audit against Endocrine Society Guidelines on the Investigation and Management of PPGL and to obtain information on other important aspects not included in these guidelines. Results: Responses were received from 58 laboratories and the data were compiled. The majority of laboratories use either urine or plasma metanephrines in first-line testing for PPGL, although a number of different combinations of biochemistry tests are utilised in different centres. All laboratories measuring metanephrines or catecholamines in-house use LC or LC-MS/MS methods. There are some marked differences between laboratories in urine metanephrines reference ranges used and sample requirements. Conclusions: There is evidence of good practice in UK laboratories (as assessed against Endocrine Society Guidelines) such as widespread use of urine/plasma metanephrines and appropriate analytical methodologies used. However, there is also evidence of variations in practice in some areas that should be addressed. [ABSTRACT FROM AUTHOR]

Catecholamine release increases in dogs with pheochromocytomas and in situations of stress. Although plasma catecholamines degrade rapidly, their metabolites, normetanephrine (NME) and metanephrine (ME), are stable in acidified urine. Our aim was to verify a human urine ELISA kit for the quantification of NME and ME in canine urine and to determine the effects on metabolite stability of sampling time (morning or midday) and day (ordinary or day spent in a clinic). We analyzed 179 urine samples from 17 healthy dogs. For NME, the mean intra-assay CV was 6.0% for all samples and 4.3% for the canine control; inter-assay CVs were 3.3, 3.8, and 12% for high and low concentration human urine positive controls supplied in the ELISA kit and a positive canine control, respectively; spike-recovery was 90–101%. For ME, mean intra-assay CV was 6.5% for samples and 9.0% for the canine control; inter-assay CVs were 12.7, 7.2, and 22.5% for high and low concentration human urine positive controls supplied in the ELISA kit and a positive canine control, respectively; spike-recovery was 85–89%. Dilution recovery was unsatisfactory for both metabolites. Based on our verification results, NME was selected for remaining analyses. We found no effect on NME concentrations of acidification or room temperature storage for up to 24 h. The NME:creatinine ratio was higher after the first of 3 clinic days compared to the same morning (111.2 ± 5.5 vs. 82.9 ± 5.3; p < 0.0001), but not on the other days. NME verification results were generally superior to ME. Dilution studies were unsatisfactory for both metabolites. Given that NME was stable without acidification at room temperature, urine samples can be collected at home. The clinic environment can cause higher NME:creatinine ratios, especially in unaccustomed dogs. [ABSTRACT FROM AUTHOR]

Accurate measurement of plasma metanephrines (MNs) including metanephrine (MN) and normetanephrine (NMN) is crucial for the screening and diagnosis in pheochromocytomas and paragangliomas (PPGLs). Although the number of laboratories using liquid chromatography tandem mass spectrometry (LC–MS/MS) method to measure MNs has been increasing rapidly, those laboratory-developed assays showed incomparable results. There are no reference measurement procedures (RMPs) or reference materials (RMs) for MNs in Joint Committee for Traceability in Laboratory Medicine (JCTLM), which hindered the standardization of MNs measurement. We established a candidate RMP (cRMP) based on isotope dilution liquid chromatography tandem mass spectrometry (ID-LC/MS/MS) method for plasma MNs measurement. Plasma samples were spiked with MN-D3 and NMN-D3 as internal standards; protein precipitation and ion-exchange solid phase extraction (SPE) were performed to extract samples, eventually analyzed by LC–MS/MS. The cRMP was applied to evaluate two routine ID-LC/MS/MS methods through split-sample comparisons. Fifty-three individual patient samples were determined by cRMP and two routine ID-LC/MS/MS methods; results were analyzed by ordinary linear regression and Bland–Altman plots. The cRMP exhibited desirable imprecision, with intra-run and total imprecision (coefficient variation, CV) for MN being 0.79–1.36% and 1.53–1.87% and for NMN being 1.10–1.34% and 1.15–1.64%. The analytical recoveries of MN and NMN ranged from 98.3 to 101.7% and from 98.5 to 101.9%, respectively. Significant calibrator biases and sample-specific deviations were observed in method comparison. An accurate, precise, and reliable cRMP for plasma MNs was developed, and RMs with value assigned following the cRMP would help minimize the calibration bias and improve the comparability of different measuring systems. [ABSTRACT FROM AUTHOR]

Background: Pheochromocytomas and paragangliomas (PPGL) are neuroendocrine tumors that originate from adrenal medulla or extra-adrenal chromaffin cells, respectively. They produce an excess of catecholamines and their metabolites. Abnormal levels of these biomolecules have been also found in pediatric patients with neuroblastoma (NB). Due to the diurnal fluctuation, the laboratory practice recommends the determination of biogenic amines in acidified 24-h urine samples. However, the collection and acidification of specimens cannot be performed easily, especially for children. Spot urines represent an attractive alternative for the detection of catecholamines and corresponding metabolites., Methods: In our study, we enrolled 50 patients with symptoms related to PPGL and we determined the concentration values for both spot and 24-h urine samples using high-performance liquid chromatography tandem mass spectrometry (HPLC/MS-MS). Since day variations of the urinary concentration are due to fluctuations in renal excretion rather than in production, we normalized the concentration of biogenic amines in spot urine and in 24-h urine collection to urinary creatinine concentration. A correlation study between the normalized levels of biogenic amines was performed using a linear regression analysis model and Pearson's correlation coefficients., Results: We obtained a good correlation of values which suggests an interchangeability of the 24-h and random urine samples. Only for epinephrine a weak correlation was determined., Conclusions: Our findings suggest that the sample collection as single spot urine may replace 24-h collection for the detection of urinary biogenic amines by HPLC/MS-MS., Competing Interests: All other authors have no conflict of interest to disclose., (Copyright 2024, Rosato et al.)

Aims: It is well‐accepted that takotsubo syndrome (TS) is characterized by a massive surge of plasma catecholamines despite lack of solid evidence. The objective of this study was to examine the hypothesis of a massive catecholamine elevation in TS by studying plasma‐free catecholamine metabolites in patients participating in the Stockholm myocardial infarction (MI) with normal coronaries 2 (SMINC‐2) study where TS constituted more than one third of the patients. Methods and results: The patients included in the SMINC‐2 study were classified, according to cardiac magnetic resonance (CMR) imaging findings (148 patients), which was performed at a median of 3 days after hospital admission. Plasma‐free catecholamine metabolites; metanephrine, normetanephrine, and methoxy‐tyramine were measured on day 2–4 after admission. Catecholamine metabolite levels were available in 125 patients. One hundred and ten (88%) of the 125 patients included in SMINC‐2 study, and 38 (86.4%) of the 44 patients with TS had completely normal plasma metanephrine and normetanephrine levels. All patients had normal plasma methoxy‐tyramine levels. Fourteen (11.2%) of the 125 patients included in SMINC‐2 study, and 5 (11.6%) of the 43 patients with TS had mild elevations (approximately 1.2 times the upper normal limits) of either plasma metanephrine or normetanephrine. One patient with pheochromocytoma‐triggered TS had marked elevation of plasma metanephrine and mild elevation of plasma normetanephrine. There were no significant differences between the number or degree of catecholamine metabolite elevations between the different groups of patients with CMR imaging diagnosis included in SMINC‐2 study. Conclusion: There was no evidence of massive catecholamine elevations in the acute and subacute stages of TS apart from one patient with pheochromocytoma‐induced TS. Most of the TS patients had normal catecholamine metabolites indicating that blood‐borne catecholamines do not play a direct role in the pathogenesis of TS. [ABSTRACT FROM AUTHOR]

Abstract Introduction We sought to characterize the prevalence and factors characteristic of head and neck paragangliomas (HNPGLs) that secrete catecholamines to inform best practices for diagnosis and management. Methods This was a retrospective cohort study from 2000 to 2020 at a single‐institution tertiary centre. One‐hundred fifty‐two patients (182 tumours) with HNPGLs with at least one measurement of urine or plasma catecholamines and/or catecholamine metabolite levels prior to treatment were included. We differentiated and characterized those patients with increased level(s) of any nature and those with ‘clinically significant’ versus ‘clinically insignificant’ catecholamine production. Results Thirty‐one (20.4%) patients had increased catecholamine and/or catecholamine metabolite levels. In most patients, these levels were ≤5‐fold above the upper limit of the reference range. Four of these 31 patients with increased levels were ultimately found to have an additional catecholamine secreting mediastinal paraganglioma or pheochromocytoma. Fourteen of 31 patients with HNPGL were deemed clinically significant secretors of catecholamines based on hyper‐adrenergic symptoms and/or profound levels of normetanephrines. This cohort was enriched for patients with paragangliomas of the carotid body or cervical sympathetic chain and those with SDHB genetic mutations. Ultimately, the prevalence of clinically significant catecholamine secreting Hangs was determined to be 9.2% and 7.7% based on a per‐patient and per‐tumour basis, respectively. Conclusions The rate of catecholamine excess in the current cohort of patients with HNPGLs was higher than previously reported. Neuroendocrine tumours of any anatomic subsite may secrete catecholamines, although not all increased laboratory level(s) are indicative of clinically significant catecholamine secretion causing symptoms or warranting adrenergic blockade.

Most cases of hypertension are because of essential hypertension, however 5% – 15% of cases can be a result of a secondary cause. In this article, we focus on the endocrine causes of secondary hypertension with a particular focus on pheochromocytomas (PCCs) and paragangliomas (PGLs). Around 15 endocrine disorders can initially present with hypertension. Amongst those PCCs and PGLs are rare but potentially life-threatening causes. An early diagnosis and timely referral can be life-saving. Herein, we present an approach for screening and diagnosis of these patients and focus on the importance of genetic testing.

Most cases of hypertension are because of essential hypertension, however 5% -- 15% of cases can be a result of a secondary cause. In this article, we focus on the endocrine causes of secondary hypertension with a particular focus on pheochromocytomas (PCCs) and paragangliomas (PGLs). Around 15 endocrine disorders can initially present with hypertension. Amongst those PCCs and PGLs are rare but potentially life-threatening causes. An early diagnosis and timely referral can be life-saving. Herein, we present an approach for screening and diagnosis of these patients and focus on the importance of genetic testing. [ABSTRACT FROM AUTHOR]

Introduction: We sought to characterize the prevalence and factors characteristic of head and neck paragangliomas (HNPGLs) that secrete catecholamines to inform best practices for diagnosis and management. Methods: This was a retrospective cohort study from 2000 to 2020 at a single‐institution tertiary centre. One‐hundred fifty‐two patients (182 tumours) with HNPGLs with at least one measurement of urine or plasma catecholamines and/or catecholamine metabolite levels prior to treatment were included. We differentiated and characterized those patients with increased level(s) of any nature and those with 'clinically significant' versus 'clinically insignificant' catecholamine production. Results: Thirty‐one (20.4%) patients had increased catecholamine and/or catecholamine metabolite levels. In most patients, these levels were ≤5‐fold above the upper limit of the reference range. Four of these 31 patients with increased levels were ultimately found to have an additional catecholamine secreting mediastinal paraganglioma or pheochromocytoma. Fourteen of 31 patients with HNPGL were deemed clinically significant secretors of catecholamines based on hyper‐adrenergic symptoms and/or profound levels of normetanephrines. This cohort was enriched for patients with paragangliomas of the carotid body or cervical sympathetic chain and those with SDHB genetic mutations. Ultimately, the prevalence of clinically significant catecholamine secreting Hangs was determined to be 9.2% and 7.7% based on a per‐patient and per‐tumour basis, respectively. Conclusions: The rate of catecholamine excess in the current cohort of patients with HNPGLs was higher than previously reported. Neuroendocrine tumours of any anatomic subsite may secrete catecholamines, although not all increased laboratory level(s) are indicative of clinically significant catecholamine secretion causing symptoms or warranting adrenergic blockade. [ABSTRACT FROM AUTHOR]