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Background: Over the past decade, the phenomenon of high urine iodine (HUI) and high water iodine (HWI) has become more common. But the risk of goiter caused by different levels of HUI and HWI remains unclear. Objectives: To explore the risk of goiter development caused by HUI and HWI, and compare the risk of goiter development from different levels of high iodine. Methods: The Medline, Cochrane library, Embase, China National Knowledge Infrastructure and Wan fang databases were searched for relevant population-based studies investigating the link between high iodine levels and goiter development in mainland China. Three reviewers extracted data from the included studies independently, assessing the prevalence of goiter development due to high iodine. Results: Taking 100 μg/L ≤ UIC < 300 μg/L (UIC = urinary iodine concentration) as the reference group, the odds ratio (OR) regarding high iodine levels and goiter formation was 1.74 (95% CI 1.50, 2.01, P < 0.001), if the water iodine concentration (WIC) was greater than 100 μg/L, the OR between goiter development and WIC was 4.74 (95% CI 1.15, 19.46, P = 0.001). The Linear trend analysis of HUI and goiter showed that the prevalence of goiter increased with the increase of UIC (χ2 = 734.605, P < 0.001). Conclusions: When the UIC ≥ 300 μg/L or the WIC ≥ 100 μg/L, the risk of goiter will increase. The higher the UIC, the greater the risk of goiter development. In order to improve the public thyroid health, we should adhere to the monitoring of urinary iodine and water iodine, and keep them at an appropriate level. Trial registration: PROSPEROCR, CRD42020197620. Registered 8 August 2020, https://www.crd.york.ac.uk/PROSPERO/. [ABSTRACT FROM AUTHOR]

Background: An alternative feasible and convenient method of assessing iodine intake is needed.Objective: The aim of this study was to examine the utility of serum iodine for assessing iodine intake in children.Methods: One blood sample and 2 repeated 24-h urine samples (1-mo interval) were collected from school-age children in Shandong, China. Serum free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), thyroglobulin (Tg), total iodine (StI), and non-protein-bound iodine (SnbI) concentrations and urine iodine (UIC) and creatinine (UCr) concentrations were measured. Iodine intake was estimated based on two 24-h urine iodine excretions (24-h UIE). Associations between serum iodine and other factors were analyzed using the Spearman rank correlation test. Receiver operating characteristic (ROC) curves were used to illustrate diagnostic ability of StI and SnbI.Results: In total, 1686 children aged 7-14 y were enrolled. The median 24-h UIC for the 2 collections was 385 and 399 μg/L, respectively. The median iodine intake was estimated to be 299 μg/d and was significantly higher in boys than in girls (316 μg/d compared with 283 μg/d; P < 0.001). StI and SnbI were both positively correlated with FT4 (ρ = 0.30, P < 0.001; and ρ = 0.21, P < 0.001), Tg (ρ = 0.21, P < 0.001; and ρ = 0.19, P < 0.001), 24-h UIC (ρ = 0.56, P < 0.001; and ρ = 0.47, P < 0.001), 24-h UIE (ρ = 0.46, P < 0.001; and ρ = 0.49, P < 0.001), urine iodine-to-creatinine ratio (ρ = 0.58, P < 0.001; and ρ = 0.62, P < 0.001), and iodine intake (ρ = 0.49, P < 0.001; and ρ = 0.53, P < 0.001). The areas under the ROC curves for StI and SnbI for the diagnosis of excessive iodine intake in children were 0.76 and 0.77, respectively. The optimal StI and SnbI threshold values for defining iodine excess in children were 101 and 56.2 μg/L, respectively.Conclusions: Serum iodine was positively correlated with iodine intake and the serum FT4 concentration in children. It is a potential biomarker for diagnosing excessive iodine intake in children. This trial was registered at clinicaltrials.gov as NCT02915536. [ABSTRACT FROM AUTHOR]

Background: The iodine nutritional status of the Chinese population has been greatly improved in recent years. Therefore, the reference values for thyroid volume (Tvol) in children with sufficient iodine intake need to be updated. The study aimed to update the reference values for Tvol in children with sufficient iodine intake in order to define goiter in the context of sustained iodine sufficiency. Methods: A cross-sectional study was conducted in children with sufficient iodine intake in China. Twice-repeated 24-hour urine samples were collected from each child to estimate habitual daily iodine intake. Serum thyroid function tests were measured. Tvol was assessed by ultrasound. From the sample of euthyroid children with sufficient iodine intakes, the 50th and 97th percentiles for Tvol by age and body surface area (BSA) were calculated using quantile regression. Results: A total of 679 children aged 8–13 years with sufficient iodine intake (188 μg/day [145–235 μg/day]) were included in the analysis. The mean Tvol of the children was 4.1 ± 1.6 mL, and no differences were found between boys and girls in any age or BSA group. Quantile regression models demonstrated that BSA was a strong positive predictor of Tvol (p < 0.0001), while age only had a significant effect on median Tvol (p = 0.013). Sex was not a significant predictor of Tvol in children. Conclusions: The reference values for Tvol in Chinese children have been updated. This study indicates that the upper limit of (97th percentile) Tvol was dependent on BSA, while the median Tvol was determined by both age and BSA. [ABSTRACT FROM AUTHOR]

To establish 24-h urinary creatinine excretion reference ranges based on anthropometry in healthy Chinese children, a cross-sectional survey was conducted using twice-sampled 24-h urine and anthropometric variables. Age- and sex-specific 24-h creatinine excretion reference ranges (crude and related to individual anthropometric variables) were derived. During October 2013 and May 2014, urine samples were collected. Anthropometric variables were measured in the first survey. Data of 710 children (377 boys and 333 girls) aged 8–13 years who completed the study were analyzed. No significant difference was observed in 24-h urine volumes between the two samples (median [interquartile range): 855.0 [600.0–1272.0) mL vs. 900.0 [660.0–1220.0) mL, P = 0.277). The mean 24-h urine creatinine excretion was regarded as representative of absolute daily creatinine excretion in children. Sex-specific, body-weight-adjusted creatinine excretion reference values were 15.3 mg/kg/day (0.1353 mmol/kg/day) for boys and 14.3 mg/kg/day (0.1264 mmol/kg/day) for girls. Differences were significant between boys and girls within the same age group but not across different age groups within the same sex. Ideal 24-h creatinine excretion values for height were derived for potential determination of the creatinine height index. These data can serve as reference ranges to calculate ratios of analyte to creatinine. The creatinine height index can be used to assess somatic protein status. [ABSTRACT FROM AUTHOR]

Background: The adverse effects of iodine excess on the thyroid in children are not well understood, and the Tolerable Upper Intake Level for iodine in children is unclear. Objectives: The aims of this study were to assess the effects of chronic long-term iodine excess on thyroid function in children and to explore the safe Tolerable Upper Intake Level of iodine in Chinese children. Design: A multistage cross-sectional study was conducted in 2224 children from areas with adequate to excessive iodine content in drinking water. Repeated samples of 24-h urine and spot urine samples were collected to estimate habitual daily iodine intakes of children. The thyroid volume in children was measured and blood samples were collected to determine thyroid function. Results: The habitual iodine intake of children was 298 µg/d (range: 186-437 µg/d). The total goiter rate was 9.7%, 232 (11.2%) children had hyperthyrotropinemia, and 232 (11.2%) children had thyroglobulin (Tg) concentrations >40 µg/L. The prevalence of hyperthyrotropinemia was >10% in children at iodine intakes of 200300 µg/d. Tg concentrations increased with increased iodine intake (β = 0.5; 95% CI: 0.4, 0.6), and the prevalence of Tg >40 µg/L was >3% in all iodine-intake groups. Multivariate logistic regression analysis indicated that the risk of total goiter significantly increased at iodine intakes ≥250-299 µg/d in 7- to 10-y-old children (OR: 8.8; 95% CI: 2.3, 34.0) and at iodine intakes ≥300-399 µg/d in 11- to 14-y-old children (OR: 5.2; 95% CI: 1.5, 18.3). However, there were no consistent differences in the risk of hyperthyrotropinemia and Tg >40 µg/L in children between different iodine-intake groups. Conclusions: Thyroid volume and goiter appear to be more sensitive indicators of thyroid stress than thyrotropin and Tg in children with long-term excess iodine intakes. We recommend 250 and 300 µg/d as safe Tolerable Upper Intake Levels of iodine for children aged 7-10 y and 11-14 y, respectively. [ABSTRACT FROM AUTHOR]

Objective To assess the validity of urinary iodine excretion ( UIE) estimated by urinary iodine/creatinine ratio ( UI/Cr) from spot urines in Chinese school-age children. Design A cross-sectional survey was performed in which twice-repeated collections of 24-h urine, and spot urine samples were obtained within 1 month. Measurements Urinary iodine concentration ( UIC), urinary creatinine concentration ( UCr), urine volume (Uvol) of spot and 24-h urine samples were measured. Measured 24-h UIE was calculated from 24-h UIC multiplied by 24-h Uvol, while the estimated 24-h UIE was calculated from spot UI/Cr multiplied by 24-h urinary creatinine excretion (24-h UCrE). Results No significant difference was observed in 24-h Uvol between two repeated collections ( P = 0·70), while spot UIC, 24-h UIC, spot UI/Cr and measured 24-h UIE were significantly different ( P < 0·05). The estimated 24-h UIE was 247 (136-431) μg/day in the first collection, lower than the measured 24-h UIE of 329 (183-536) μg/day ( P < 0·001), while no significant difference was observed ( P = 0·30) in the second sampling as the estimated 24-h UIE was 355 (168-624) μg/day and the measured 24-h UIE 350 (181-615) μg/day. The spot UIC ( r = 0·57, P < 0·001), spot UI/Cr ( r = 0·63, P < 0·001) and the estimated 24-h UIE ( r = 0·83, P < 0·001) were strongly correlated with the measured 24-h UIE in the first collection. Likewise, in the second sampling, spot UIC ( r = 0·60, P < 0·001), spot UI/Cr ( r = 0·72, P < 0·001) and the estimated 24-h UIE ( r = 0·89, P < 0·001) were also correlated with measured 24-h UIE. The Bland-Altman results indicated 95% of subjects were expected to locate within the limits of agreement ( LOA), but showed an underestimation of the urinary iodine excretion by the estimated 24-h UIE. In addition, moderate-to-good agreement was found for the estimated and measured 24-h UIE, with kappa values of 0·55 and 0·66. Conclusions Estimated 24-h UIE by UI/Cr ratio from spot urine could represent a valid and reliable alternative for measured 24-h UIE in estimating iodine excretion in children. [ABSTRACT FROM AUTHOR]

Background: Variation in different urinary measurements for evaluation of iodine status is of concern to clinicians and researchers.Objective: This study evaluated variations between urine iodine concentration (UIC), spot and 24-h urine sample creatinine concentrations, and 24-h urine iodine excretion (24-h UIE) in repeated samples from school-age children.Methods: Urine samples (24 h and morning spot) were collected on 2 occasions from 981 children in Ningjin and Lingxian counties, China. Samples from Ningjin were collected in October and November 2013, and samples from Lingxian were collected in April and May 2014. Morning spot urine iodine concentration (MUIC), morning spot urine creatinine, 24-h UIC, and 24-h urine creatinine were measured in all samples. The 24-h UIE was calculated by multiplying the 24-h UIC by the 24-h urine volume.Results: In Ningjin County, the 24-h UIC and 24-h UIE did not differ between repeated collections [192 and 172 μg/L, respectively, for 24-h UIC (P = 0.08); 123 and 120 μg/L, respectively, for 24-h UIE (P = 0.56)], whereas the MUIC was lower in November 2013 than in October 2013 (170 and 190 μg/L, respectively; P = 0.034). In Lingxian County, no significant differences were observed in 24-h UIC between the repeated collections (230 and 218 μg/L, respectively; P = 0.79), whereas the 24-h UIE and MUIC were higher in the samples collected in May 2014 than in April 2014 [161 and 155 μg/L, respectively, for 24-h UIE (P = 0.002); 244 and 203 μg/L, respectively, for MUIC (P < 0.001)]. When data from both counties were combined, no difference was observed between repeated 24-h UIC (214 compared with 196 μg/L; P = 0.17) and 24-h UIE (143 compared with 143 μg/d; P = 0.06), but MUICs were lower in the first collection than in the second collection (199 and 207 μg/L, respectively; P = 0.002). The κ values were >0.4 for 24-h UIC and mean UIE, whereas relatively low κ values were observed for MUIC and mean UIE.Conclusion: The 24-h UIC was more accurate and reproducible than the MUIC in evaluating iodine status in a large-scale population study of school-age children. [ABSTRACT FROM AUTHOR]

Iodine deficiency is a global issue that is correlated with a variety of diseases and can affect individuals of all ages. We hypothesized that a general, semiquantitative food frequency questionnaire (FFQ) could be a valuable tool to evaluate iodine intake in children. Study participants comprised 687 healthy children between the ages of 7 and 13 years. The FFQ was developed to assess habitual iodine intake over a 6-month period (FFQ1). A 3-day estimated food diary (3DEFD) and the habitual daily iodine intake, calculated from 2-repeated 24-hour urine iodine excretion, tested the intermethod relative validity of the FFQ. There were 92 children who also repeated the FFQ (FFQ2) 3 weeks later to assess for FFQ reproducibility. Iodine intake estimated by FFQ1 + water was significantly higher than that indicated by the 3DEFD + water (204 μg/d vs 156 μg/d, P < .001), whereas there were no differences between habitual daily iodine intake and FFQ1 + water (185 μg/d vs 204 μg/d, P = .223). The interclass correlation coefficients of iodine intake estimated by the FFQ1 and FFQ2 were 0.72 ( P < .001). The FFQ1 + water was moderately correlated with the 3DEFD + water (Spearman correlation coefficient = 0.57, P < .001) as well as habitual daily iodine intake (SCC = 0.34, P < .001). The subjects classified into the same or adjacent quartiles ranged from 32% to 93%. The κ value α was 0.46 for FFQ1 and FFQ2 ( P < .001) 0.27 for FFQ1 + water and 3DEFD + water ( P < .001), and 0.09 for FFQ1 + water and habitual daily iodine intake ( P < .001). The results showed this FFQ is a reliable and reproducible tool in evaluating iodine intake in Chinese children. [ABSTRACT FROM AUTHOR]