Indirect reference intervals for TSH in a sample of lebanese pregnant women

Background

Thyroid dysfunction in pregnant women can lead to fetal complications. Thyroid-stimulating hormone (TSH) is the key hormone for diagnosis of thyroid dysfunction. No previous study has established reference intervals (RI) for TSH in Lebanese pregnant women. The objective of this study is to define the TSH RIs for each trimester of pregnancy in healthy Lebanese pregnant women using an indirect method.

Materials and methods

This retrospective study included 287 pregnancies selected from the records of an obstetric clinic at Hôtel-Dieu de France University Hospital from January 2021 to May 2023. A control group of 103 non-pregnant women was also included in the study. The collected TSH values were stratified by trimester (first and second) of pregnancy and postpartum. After applying the exclusion criteria, a total of 458 TSH values were included in the analysis.

Results

The respective medians and RIs for TSH during the first, second pregnancy trimesters and postpartum are 1.57 (0.43–3.20 mIU/L), 1.84 (0.56–4.41 mIU/L), and 1.38 (0.30–3.60 mIU/L), while for the control group it is 1.66 (0.64–4.24 mIU/L). There is a significant correlation between TSH values in the first trimester and those in the second trimester and postpartum (p ≤ 0.001 and p = 0.002 respectively). No significant correlation was observed between age and TSH levels in the first and second trimesters and as well as in postpartum.

Conclusion

Our RIs are close to the revised American Thyroid Association (ATA) recommendations. Further research is needed to understand the mechanisms and clinical impact of these differences.