Background and objectives: This study was undertaken to evaluate the status of iodine nutrition and thyroid function of women at different phases of gestation in an iodine sufficient rural area.
Methods and study design: 215 pregnant women in different trimesters were consecutively enrolled in iodine sufficient rural areas of Yongjing county of Gansu province, China. The blood samples and random urine samples were collected from them, and serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxin (FT4), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb) and urinary iodine were measured.
Results: Median Urinary Iodine (MUI) of three groups of pregnant women (first, second and third trimester) were 190 μg/L, 153 μg/L and 145 μg/L respectively. With the increase of gestational age, the level of FT3 decreased. And the FT3 level in the first trimester was higher than those in the second and third trimester. There was a U-shaped curve seen between the TSH levels and the gestational age. The medians of TgAb and TPOAb appeared the lowest in the first trimester．Significant difference was seen in TgAb and TPOAb levels of the three groups of pregnant women. The incidence of thyroid function disorder was 1.86%, including subclinical hypothyroidism accounted for 1.40% and hypothyroidism accounted for 0.47%. The incidence of thyroid function disorder mainly appeared in the early pregnancy. Abnormal FT3, TSH, positive TgAb and TPOAb were mainly seen during early pregnancy.
Conclusions: The levels of serum TSH and thyroid hormones fluctuate at the different phases of pregnancy. With the increase of gestational age, the incidence of iodine deficiency also increased. Abnormal thyroid hormones, TSH, positive TgAb and TPOAb were mainly existed in the early pregnancy.