An Evaluation of the Second Trimester Thyroid Function Test in Gestational Diabetes Mellitus: A Case-Control Study

Area of Science:

• Endocrinology
• Obstetrics
• Immunology

Background:

• Gestational diabetes mellitus (GDM) is glucose intolerance during pregnancy, increasing risks for maternal and infant complications.
• Maternal thyroid function changes in early pregnancy are associated with GDM risk.
• Hypothyroidism during pregnancy can lead to adverse outcomes, including miscarriage, hypertension, and impaired infant development.

Purpose of the Study:

• To compare thyroid function tests (serum fT3, fT4, TSH) and thyroid peroxidase antibody (anti-TPO) levels between GDM and non-GDM pregnant women in the second trimester.
• To correlate adverse pregnancy outcomes with thyroid function tests in both GDM and non-GDM groups.

Main Methods:

• A nested case-control study involving 350 pregnant women (13-28 weeks gestation) was conducted.
• 40 GDM and 40 non-GDM women were selected based on oral glucose tolerance test (OGTT) results.
• Thyroid function tests (TFTs) and anti-TPO antibodies were compared; sociodemographic data and pregnancy outcomes were analyzed.

Main Results:

• Women with GDM were older on average than non-GDM women.
• Significantly lower mean TFT values (fT3, fT4, TSH) were observed in the GDM group compared to the non-GDM group.
• Higher anti-TPO antibody levels, indicative of thyroid autoimmunity, were found in the GDM group, potentially contributing to insulin resistance.

Conclusions:

• The study suggests a significant association between altered thyroid function and GDM.
• While maternal complications like polyhydramnios and preterm labor were more frequent in the GDM group, statistical significance was not reached.
• A higher incidence of Cesarean delivery was noted in the GDM group, supporting the recommendation for routine TFT screening in at-risk pregnancies.