Study on iodine level and thyroid disease prevalence of pregnant female in Zhenjiang area of Jiangsu Province

  Objective  To analyze the iodine nutrition level of pregnant female in Zhenjiang area and the incidence of thyroid diseases during pregnancy, so as to provide the basis for formulating the appropriate iodine nutrition standard during pregnancy.

  Methods  A total of 467 pregnant female were selected by stratified cluster random sampling. Serum free triiodothyronine (FT₃), free thyroxine (FT₄), thyroid stimulating hormone (TSH), thyroid peroxidase antibody (TPOAb), thyroid globulin antibody (TgAb) and urinary iodine were detected. The association between iodine level and thyroid disease in pregnant female in the region was analyzed.

  Results  The median urinary iodine concentration (UIC) of pregnant women was 124.1 μg/L, and mild iodine deficiency was found in the first trimester (T₁ stage), second trimester (T₂ stage) and last trimester (T₃ stage) of pregnancy. The prevalence of subclinical hypothyroidism in T₁ stage was significantly higher than that in T₂ and T₃ stages (P < 0.001). The prevalence of hypothyroxinemia (T₄) in T₂ and T₃ stage was significantly higher than that in T₁ stage (P < 0.05). After controlling for age, gestational age and other factors, the risk of subclinical hypothyroidism of UIC 250~ < 500 μg/L was 2.65 times higher than that of UIC 150~ < 250 μg/L (P < 0.05); the risk of subclinical hypothyroidism with UIC≥500 μg/L was 4.97 times higher than that with UIC 150~ < 250 μg/L(P < 0.05), and 3.65 times higher than that with UIC 50~150 μg/L(mild and moderate iodine deficiency) (P < 0.05). The level of FT₄ in T₁ stage with UIC≥250 μg/L was significantly lower than that of UIC 150~ < 250 μg/L and UIC 50~150 μg/L (P < 0.01).

  Conclusion  After the implementation of the new standard of iodized salt, the famale in different stages of pregnancy in this region are in a state of mild iodine deficiency. UIC≥250 μg/L(especially UIC≥500 μg/L) can significantly increase the risk of subclinical hypothyroidism during pregnancy. Therefore, reasonable iodine levels and regular monitoring should be maintained during pregnancy.