Larger Thyroid Volume and Adequate Iodine Nutrition in Chinese Schoolchildren: Local Normative Reference Values Compared with WHO/IGN.

Objective. Thyroid volume measured by ultrasound to define goiter needs reliable local thyroid volume reference from iodine-sufficient populations. The aim of this study is to explore the reference interval for normal thyroid volume in schoolchildren aged 8-10 years from Zhejiang Province, China. Methods. A probability-proportionate-to-size sampling method was applied to select a representative sample of 1213 children aged 8-10 years in Zhejiang Province to detect the thyroid volume, salt iodine, and urine iodine. Results. Median urinary iodine concentration in involved schoolchildren was 178.30 (125.00) μg l-1, with the percentage of samples less than 100 μg l-1 as 12.69% and more than 300 μg l-1 as 15.25%. Thyroid volume was significantly correlated with age and anthropometric measurements independently of each other. The 97th percentile of thyroid volume in our study was larger generally than the new international reference. Conclusions. The iodine nutritional status in Zhejiang Province was at an adequate level. Despite some limitations in this study, we initially established the reference values for thyroid volume in 8-10-year-old schoolchildren in Zhejiang Province, China, as a local reference to be used for monitoring iodine deficiency disorders.