In children with sonographic signs of AIT from the settlements of Vitebsk and Minsk regions, a reduced content of both iodine and selenium and zinc in the body was revealed, which is a distinctive feature of microelement provision from healthy children. The content of selenium and iodine in the hair of this group of children is 1.52 times lower than in the group of healthy children and 2-3 times lower than the lower indicators of normative values. The low content of iodine in the body is due to the insufficient intake of iodized salt in 50-60 % of the surveyed school children and pregnant women in almost all the regions surveyed. In children with sonographic signs of AIT, a pronounced iodine-selenium-zinc deficiency has been established, which may be one of the reasons for the decrease in the level of antioxidant protection of the body and one of the main factors responsible for the formation of AIT in various regions of Belarus.