Impact of removing iodised salt on children's goitre status in areas with excessive iodine in drinking-water.

The impact of removing iodised salt on children's goitre status in a high-iodine area (HIA) remains unclear. The aim of the present study was to explore the changes in the prevalence of goitre in children after removing iodised salt from their diet. For this purpose, three towns with the median water iodine content of 150-300 mu g/l were selected randomly in Hengshui City, Hebei Province, China. A total of 452 and 459 children were randomly selected from the three towns in order to measure thyroid volume by ultrasound before and after removing iodised salt, respectively. Their goitre status was judged using the criteria of age-specific thyroid volume recommended by the WHO. After removing iodised salt, the overall median urinary iodine content (MUIC) of children decreased from 518 (interquartile range (IQR) 347-735) to 416 (IQR 274-609) mu g/l. The MUIC of children across sex and age group decreased significantly except for the age group of 9 years. The overall prevalence of goitre in the three towns significantly decreased from 24.56% (n 111/452) to 5.88% (n 27/459) (P<0.001). Goitre prevalence in children aged 8-10 years decreased from 33.70% (n 31/92), 23.32% (n 45/193) and 20.96% (n 35/167) to 6.10% (n 10/164), 5.52% (n 9/163) and 6.06% (n 8/132), respectively. Goitre prevalence in boys and girls decreased from 27.05% (n 66/244) and 21.63% (n 45/208) to 6.66% (n 15/226) and 5.15% (n 12/233), respectively. The decreases in the prevalence of goitre in children across sex and age group were all statistically significant. The present study revealed that goitre prevalence in children decreased significantly after removing iodised salt from their diet for about 1.5 years in the HIA in Hebei Province.