Three hundred pregnant women and 300 women of reproductive age (controls) were selected from regions with a dietary iodine excess to evaluate thyroid and autoimmune thyroid functions. Fasting morning urine and venous blood samples were collected. Urinary iodine concentration, serum free tri-iodothyronine (FT3), free thyroxine (FT4), sensitive thyroid stimulating hormone (sTSH), serum thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TGAb) levels were determined. Iodine levels were excessive in 83.7% of pregnant women and 80.7% of the control women. The former showed lower rates of total thyroid disease and subclinical hypothyroidism than the latter (21.7% vs 29.7%, P < 0.05; 19.7% vs 27.3%, P < 0.05). The FT3 level, FT4 level, and TGAb positive rate of pregnant women were lower than that in the controls (P < 0.05). Thus, both excessive iodine intake and pregnancy can influence the thyroid and autoimmune thyroid functions of women.
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