Status of thyroid function and intelligence quotient of children in areas with different iodine nutrition levels in Xinjiang Uygur Autonomous Region / 中华地方病学杂志

ABSTRACT

Objective:To learn about the status of thyroid function and intelligence quotient (IQ) of children in areas with different iodine nutrition levels in Xinjiang Uygur Autonomous Region, and to explore the health risk of children with median urinary iodine of 200 - 299 μg/L, and to provide a basis for scientific iodine supplementation.Methods:In May 2019, in Xinjiang Uygur Autonomous Region, Altay Prefecture and Kashgar Prefecture were selected, where the median urinary iodine of children aged 8 to 10 years were 100 - 199 and 200 - 299 μg/L for three consecutive years (2017 - 2019). A stratified random sampling method was used to select 400 children aged 8 to 10 years in each of the two regions, urine and blood samples were collected to detect urinary iodine and thyroid function [thyrotropin stimulating hormone (TSH), free thyroxine (FT 4), free triiodothyronine (FT 3), anti-thyroglobulin antibody (TgAb), and anti-thyroperoxidase antibody (TPOAb)]. At the same time, children's IQ was measured and determined by Second Revision of Combined Raven's Test (CRT-C2) in China and Second Revision of Combined Raven's Test for Children-the Rural, in China (CRT-RC2). Results:The median urinary iodine of children aged 8 to 10 years in Altay Prefecture and Kashgar Prefecture was 188.6 and 250.1 μg/L, respectively. There was no statistically significant difference in thyroid function indexes TSH and FT 3 levels between the two regions ( Z = - 0.58, t = 0.49, P > 0.05), while there was statistically significant difference in FT 4 level ( t = 60.08, P < 0.001). There was no statistically significant difference in TgAb positive rate [3.6% (14/394), 4.0% (16/399)] between the two regions (χ 2 = 0.11, P = 0.736), but the difference of TPOAb positive rate [9.6% (38/394), 30.6% (122/399)] was statistically significant (χ 2 = 53.93, P < 0.001), while the difference of dual antibody positive rate [0.8% (3/394), 2.0% (8/399)] was not statistically significant ( P = 0.134). There was no statistically significant difference in the detection rates of subclinical hypothyroidism [8.9% (35/394), 11.0% (44/399)], subclinical hyperthyroidism [1.0% (4/394), 1.3% (5/399)] and hyperthyroidism [0.3% (1/394), 0.8% (3/399)] in children between the two regions ( P > 0.05). The IQ results of children in the two regions were 96.55 ± 11.36 and 89.57 ± 12.35, respectively, and there was no significant difference between them ( t = 2.79, P = 0.095). Conclusions:The thyroid function status of children is similar in the two regions with median urinary iodine of 100 - 199 μg/L and 200 - 299 μg/L in children aged 8 to 10 years, but the TPOAb positive rate is significantly different. Children whose iodine nutritional level is at or above the appropriate level have no obvious changes in intelligence. It is suggested that median urinary iodine at 200 - 299 μg/L is a relatively safe iodine nutrition state.