Establishment of reference range for thyroid hormones in normal pregnant women in China's coastal area

Abstract

Purpose: The current study aims to establish reference ranges for thyroid hormones in normal pregnant women during their pregnancy period. Materials and Methods: A one-time cross-sectional survey was conducted on 490 normal pregnant women and 51 non-pregnant women (control). The serum thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free tetraiodothyronine (FT4) levels were measured. Results: The serum FT3 and FT4 levels in pregnant women decreased gradually from the first to the last three months of pregnancy (p < 0.01). The serum TSH level increased gradually during the whole pregnancy (p < 0.01), and was significantly lower than the control (p < 0.01) in the first three months. However, in the middle and last three months of pregnancy, TSH was higher than the control (p < 0.01). Conclusions: The thyroid hormone levels in normal pregnant women are different from those in non-pregnant women; significant differences exist among the three stages of pregnancy.