Effect of reducing iodine excess on children's goiter prevalence in areas with high iodine in drinking water.

The purpose of the study was to evaluate the effect of removing iodized salt on children's goiter prevalence in high iodine area (HIA). A total of 452 and 459 children aged 8-10 years old were selected by simple random sampling method before and after removing iodized salt from their diet in three towns with median water iodine content of 150-300 µg/l in Hengshui city of Hebei province of China. Their goiter status was judged using the thyroid volume (Tvol) reference for body surface area recommended by the WHO. After removing iodized salt, children's overall median urinary iodine content (MUIC) decreased from 518 (IQR 347,735) µg/l to 416 µg/l (IQR 274,609). Children's MUIC across sex and age group decreased significantly. The overall goiter prevalence in the three towns significantly decreased from 32.96 % (149/452) to 6.54 % (30/459) (P < 0.001). The goiter prevalence in 8-, 9-, and 10-year-old children decreased, respectively, from 38.04 % (35/92), 30.57 % (59/193), and 32.93 % (55/167) to 6.10 % (10/164), 6.75 % (11/163), and 6.82 % (9/132). The goiter prevalence in boys and girls decreased from 34.01 % (83/244) and 31.73 % (66/208) to 6.19 % (14/225) and 6.87 % (16/234), respectively. The decreases in children's goiter prevalence across gender and age groups were all statistically significant. The present study revealed that children's goiter prevalence decreased significantly after removing iodized salt from their diet for about one and half years in the HIA in Hebei province.