Thyroid function test reference ranges in the first trimester of gestation and pregnancy outcomes: Protocol and preliminary results for cohort population?based study Isfahan, Iran

Tis paper presents the protocol and primary fndings of pregnancy cohort population?based study in Isfahan,
Iran. In this cohort, 418 pregnant and 438 nonpregnant women were enrolled. In the frst phase, serum
concentrations of thyroid?stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), thyroid peroxidase antibody,
and urinary iodine concentration (UIC) were measured. Furthermore, the thyroid ultrasound was also performed. According to the results of thyroid function tests in the frst phase, local reference range for TSH, FT4, and FT3 in pregnant and nonpregnant women are determined. Te 2.5th and 97.5th percentiles are determined as limits of the reference ranges. In the second phase, all pregnant women underwent prenatal care visits in each trimester and they followed for 7 days after delivery and the pregnancy outcomes
data are reported. Te mean ± standard deviation for TSH, FT4, FT3, and UIC in the frst trimester of gestation was 1.84 ± 1.32 mIU/L, 1.01 ± 0.15 ng/dL, 4.50 ± 0.64 pmol/L, and 172.0 ± 90.29 ?g/L, respectively. In nonpregnant women, these values for TSH, FT4, FT3, and UIC were 2.58 ± 1.77 mIU/L, 1.10 ± 0.21 ng/dL, 4.49 ± 0.57 pmol/L, and 190.0 ± 109.6 ?g/L, respectively. Te results of the present study could contribute to establish a local thyroid function tests reference ranges in the frst trimester of pregnancy. It could possibly be e?ective on making a local reference value to prevent of thyroid disease misdiagnosis
during pregnancy and adverse pregnancy outcomes.