Assessment of the association of high-iodine exposure in drinking water, iodine intake, and thyroid function in 3−14-year-old children

Drinking water with a high iodine content is one of the sources of iodine intake, And excessive iodine intake can affect thyroid function. This study aims to investigate the effects of long-term exposure to iodine-rich groundwater on iodine intake And thyroid function in children. We recruited a total of 3,216 children aged 3-14 years on multiple occasions from 2013 to 2023 from counties with high groundwater iodine concentrations in Shandong Province, China. We collected drinking water samples to measure water iodine concentration (WIC), spot urine samples And 24-hour (24-h) urine samples to examine the iodine status. We measured the thyroid volume and collected fasting blood and dried blood spot samples to examine the thyroid function. The median WIC of children's drinking water was 183 (IQR 70.0-362) µg/L. Within each age group, all iodine indicators, including urine iodine concentration And 24-hour urine iodine excretion, etc., and thyroid volume increased significantly with increasing water iodine concentration. The odds ratios (ORs) of the impact of drinking water with iodine concentration > 300 µg/L on hyperthyrotropinemia And goiter were 1.77 (95% confidence interval [CI], 1.20-2.62) And 4.19 (95% CI, 2.68-6.57), respectively. In children, prolonged exposure to an environment with high groundwater iodine content is associated with an increase in thyroid volume, a higher prevalence of goiter, and an increased risk of hyperthyrotropinemia. Continued efforts to reduce iodine concentration in drinking water are necessary.