Evaluation of Thyroid Function and Its Relation to Glycemic Status in Pregnant Women With Gestational Diabetes Mellitus

Background Gestational diabetes mellitus (GDM) is a prevalent complication during pregnancy that can lead to adverse outcomes for both the mother and the fetus. It also increases the likelihood of developing type 2 diabetes mellitus (T2DM) later in life. Thyroid hormones play an essential role in regulating growth and metabolism and often coexist with diabetes mellitus (DM), affecting glucose metabolism. Pregnant women with GDM frequently exhibit thyroid issues, impacting insulin secretion and beta-cell function. Aim This study aims to assess thyroid function and glycemic status in pregnant women with and without GDM and to evaluate the correlation between thyroid function and glycemic status in pregnant women with GDM. Methods This prospective case-control study was conducted over two months at a tertiary care hospital in Puducherry, India. It included 60 cases (pregnant women with GDM, blood glucose > 140 mg/dL per DIPSI guidelines) and 60 age- and parity-matched controls. Blood samples were collected, centrifuged, and analyzed for blood glucose and serum thyroid levels (FT3, FT4, thyroid-stimulating hormone (TSH)) using the Cobas e-411 autoanalyzer through an electrochemiluminescence assay. Results Serum plasma glucose levels were significantly higher in cases (159.25 ± 16.22 mg/dL) compared to controls (101.6 ± 17.30 mg/dL) (p < 0.05). FT3 levels were higher in cases (3.98 ± 4.18) compared to controls (2.87 ± 0.54) (p = 0.04). The FT3/FT4 ratio was also higher in cases (3.99 ± 4.927) than in controls (2.70 ± 0.58) (p = 0.04). No significant differences were found in FT4 or TSH levels between the groups. Correlation analysis revealed no significant correlations between plasma glucose levels and thyroid function parameters. Conclusion Pregnant women with GDM showed significantly higher plasma glucose levels, FT3 levels, and FT3/FT4 ratio compared to normal pregnant women. These findings suggest an association between altered thyroid function, particularly higher FT3 levels and the FT3/FT4 ratio, and GDM.