Reference Interval of Thyroid Stimulating Hormone and free Tetra-iodothyronine in Healthy Pregnant Women of Quetta, Baluchistan

Objective: To establish the reference intervals of thyroid stimulating hormone and free Tetraiodothyronine in healthy pregnant women of Quetta, Baluchistan. Study Design: Cross-sectional study. Study Setting and Duration: Combined Military Hospital, Quetta Pakistan, at Jun 2018 to Jun 2019.Methodology: Consecutive blood samples of healthy pregnant women (in all three trimesters) were taken to analyse thyroid stimulating hormone and free Tetra-iodothyronine by electrochemiluminescence immunoassay. For all three trimesters, the 5th and 95th percentiles were taken as reference intervals of thyroid stimulating hormone and free Tetraiodothyronine. Results: A total of 388 blood samples were taken. Of these, 136 samples were from the first trimester. The mean age of the study population was 25.1±3.7 years in the first trimester, 26.7±4.5 years in the second trimester, and in the third trimester, it was 26.8±4.8 years. The reference interval for thyroid stimulating hormone in the first trimester was 0.6-3.3 uIU//ml, while it was 0.6-3.8uIU/ml and 0.6- 2.7uIU//ml during the second and third trimesters, respectively. Similarly, in the first-trimester reference interval for free Tetraiodothyronine was 9.8-18.0pmol/l. The values of free Tetraiodothyronine in the second and third trimesters were 10.4-20.1pmol/l and 11.0-20.9pmol/l, respectively. Conclusion: All laboratories should establish reference intervals for thyroid stimulating hormone (TSH) to avoid misdiagnosing thyroid disorders during pregnancy.