Establishment and application of reference ranges of thyroid function in relation to pregnancy in Hubei

Objective This study aims to establish a reference range of thyroid function indicators for women in different periods of pregnancy in Hubei Province. Methods Using the prospective method, 1 487 healthy pregnant women who did pregnancy check-up at Wuhan Maternal and Child Healthcare Hospital from March 2017 to May 2018 were asked to complete questionnaires and whose serum samples were examined, aged (29 ± 4) years within the range of 20 - 41, include 498 in early pregnancy, 525 in middle pregnancy, and 464 in late pregnancy.Then their thyroid stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) levels were determined using chemiluminescence immunoassay method to establish reference ranges of the indexes of thyroid function, reference ranges were in median (M) and percentage (P2.5 - P97.5). At the same time, the newly established reference range was compared with the reference range recommended by the American Thyroid Association (ATA) guidelines to evaluate the thyroid function of 10 232 pregnant women in counties (cities, districts) of Hubei Province. Results Reference ranges in early pregnancy, middle pregnancy and late pregnancy were shown as follows, TSH: 1.41 (0.19 - 4.26), 1.45 (0.25 - 4.39), 2.04 (0.51 - 5.10) mU/L; FT3: 4.76 (3.78 - 16.01), 4.65 (3.72 - 5.91), 4.22 (3.41 - 5.33) pmol/L; FT4: 63.71(47.40 - 86.25), 58.28 (41.18 - 82.36), 48.95 (33.41 - 66.82) nmol/L. The thyroid function assessment of pregnant women with the newly established reference range shows that the detection rate of thyroid dysfunction in pregnant women is was 13.58% (1 390/10 232), which was lower than 37.98% (3 886/10 232, χ2 = 102.58, P < 0.05) diagnosed by the ATA guidelines. Conclusions The reference range of women's specific thyroid function indicators in different stages of pregnancy in Hubei Province is established. Compared with the reference range recommended by ATA, it is more suitable for thyroid function monitoring and thyroid disease screening for pregnant women in Hubei Province. Key words: Pregnant women; Thyrotropin; Triiodothyronine; Thyroxine; Reference range