Association of Serum Thyroid Profile and Glycated Hemoglobin Levels in Diabetic Patients: A Cross-Sectional Study

Introduction Diabetes mellitus (DM) is a chronic metabolic disorder frequently associated with thyroid dysfunction and lipid abnormalities, which may worsen glycemic control and increase cardiovascular risk. The interplay between thyroid hormones and glucose metabolism is especially important in patients with type 2 diabetes mellitus (T2DM). This study was conducted to assess whether thyroid hormone levels (TSH, total T3, total T4) differ between diabetes and matched controls and whether they correlate with HbA1c within groups and comparison of lipid profiles between groups. Methods A cross-sectional study was conducted at Tezpur Medical College and Hospital, Assam, India, including 100 diabetic patients and 100 age- and sex-matched non-diabetic controls. Blood samples were analyzed for HbA1c, thyroid-stimulating hormone (TSH), total triiodothyronine (T3), total thyroxine (T4), and lipid profile using standard automated analyzers. Statistical analysis included Student's t-test, Pearson correlation, and multiple linear regression. Results Diabetic patients had significantly higher levels of HbA1c, total cholesterol, triglycerides, low-density lipoprotein (LDL), and very-low-density lipoprotein (VLDL) compared to controls. Total T3 and total T4 levels were significantly lower in diabetics, while TSH levels showed a non-significant increasing trend. HbA1c correlated negatively with total T3 and total T4 and positively with lipid parameters. All statistical analyses were done with the help of Microsoft Excel and Jamovi software. Conclusion In this study, cases with diabetes had lower total T3 and T4 levels than healthy controls, but their TSH levels were the same. HbA1c exhibited only weak correlations with thyroid indices, suggesting an absence of a robust glycemic-thyroid association in this dataset. Routine screening for lipid abnormalities may help improve metabolic control and reduce complications in diabetic patients.