Correlation of Thyroid Hormone Levels with Insulin Resistance in Newly Diagnosed Hypothyroidism

Abstract

Background: Hypothyroidism is associated with several metabolic abnormalities, including insulin resistance (IR), which increases the risk of type 2 diabetes mellitus and cardiovascular disease. This study evaluated the correlation between thyroid hormone levels and insulin resistance in patients with newly diagnosed hypothyroidism.

Methods: A hospital-based cross-sectional study was conducted among 90 newly diagnosed hypothyroid patients. Demographic and clinical data were recorded, and fasting blood samples were analysed for thyroid-stimulating hormone (TSH), free triiodothyronine (free T3), free thyroxine (free T4), fasting blood glucose, and fasting serum insulin. Insulin resistance was assessed using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Correlation analysis and multiple linear regression were performed to identify predictors of insulin resistance.

Results: The mean age of the participants was 41.8 ± 12.6 years, and 68.9% were females. The mean HOMA-IR was 3.98 ± 1.72, with 73.3% of patients demonstrating insulin resistance. Serum TSH showed a significant positive correlation with HOMA-IR (r = 0.621, p <0.001), whereas free T3 (r = −0.441, p <0.001) and free T4 (r = −0.514, p <0.001) showed significant negative correlations. Multiple linear regression identified TSH and BMI as independent positive predictors, while free T3 and free T4 were independent negative predictors of HOMA-IR.

Conclusion: Insulin resistance is highly prevalent in newly diagnosed hypothyroidism and is significantly associated with the severity of thyroid dysfunction. Early assessment of insulin resistance may help identify patients at increased metabolic risk and facilitate timely therapeutic intervention.