Correlation of thyroid function and iodine nutritional status among pregnant women of Han nationality in Urumqi

Objective To establish reference interval of thyroid hormones in pregnant women in Urumqi, standardize the diagnostic criteria of thyroid diseases in pregnancy, assess the iodine nutrition and thyroid function at different stages of pregnancy, and provide evidence to guide iodine supplementation. Methods A cross-sectional survey was performed in 3 731 pregnant women in Urumqi from May 2015 to June 2016. 1 206 of them were in the first trimester, 1 125 in the second and 1 400 in the third. 500 non-pregnant women were recruited as controls. Levels of serum thyrotrophin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), anti-thyroid peroxidase (anti-TPO) and antithyroglobulin (anti-TG) were measured, and urinary iodine levels were detected by arsenic-cerium catalytic spectrophotometry. Results There were statistically significant differences between the pregnant groups and the control group in FT3, FT4, and TSH levels (P 0.05). Conclusions Iodine nutritional status was closely related to gestational age. Abnormal TSH levels were mainly observed in the second and third trimesters, abnormal serum levels of FT3, FT4, anti-TG and anti-TPO in the first trimester, and iodine deficiency in the third trimester. Thyroid function and urinary iodine should be monitored at each trimester during pregnancy. Key words: Pregnant women; Thyroid function tests; Reference interval; Urinary iodine