Investigation of thyroid function change and urinary iodine standard of pregnant women / 中华地方病学杂志

ABSTRACT

Objectives To study the changes of thyroid function under different urinary iodine levels and pregnant trimesters,and to investigate the urinary iodine standard of pregnant women,taken thyroid function as a golden standard.Methods Early,mid and late trimester pregnant women in the iodine deficient rural areas of Gansu and Jilin Provinces were selected,at least 70 cases were included for each trimester in each province.Pregnant women included were physically healthy;cases should be excluded if their immediate relatives had a thyroid disease history.Urinary iodine,free triiodothyronine (FT3),free thyroxine (FT4),thyroid stimulating hormone (TSH),thyroid peroxidase antibody (TPOAb),thyroglobulin antibody (TgAb),and edible salt iodine from pregnant women's home were tested.The urinary iodine was measured with the method for determination of iodine in urine by As3+-Ce4+ catalytic spectrophotometry (WS/T 107-2006).Thyroid function was tested by chemiluminescence method,salt iodine was determined by direct titration method (GB/T 13025.7-1999).Results Totally 439 pregnant women were investigated in the two provinces.Median of urine iodine was 178.6 μg/L;for the 215 women in Gansu,the value was 156.4 μg/L;for the 224 women in Jilin,the value was 206.4 μg/L.Along with the increase of urinary iodine,the FT3 of Gansu decreased from 5.77 pmol/L to 5.34 pmol/L,TSH increased from the lowest 2.63 mU/L to 3.75 mU/L;the FT3 of Jilin increased from 4.41 pmol/L to 4.45 pmol/L,TSH increased from the lowest 0.92 mU/L to 1.50 mU/L.Five indicators of thyroid function of more than 97％ pregnant women were in normal range and FT3 was the most stable in the three trimesters.FT3 of the three triimesters in Gansu was 6.27,5.76,5.28 pmol/L,respectively,and that in Jilin was 4.50,4.42,4.32 pmol/L,respectively.The 5％ and 95％ quantile were 55.24,581.27 μg/L of urinary iodine,of pregnant women with normal thyroid function.Conclusions Under different urinary iodine levels,pregnant women's thyroid function is relatively stable.TSH has showed an increasing trend with increasing iodine level.Along with the progress of pregnancy,the urinary iodine is different among the three pregnancy periods,but the thyroid function is stable.The pregnant women with normal thyroid function have a urinary iodine level between 50-600 μg/L.