Background: Increased risk of atherosclerosis and cardiovascular disorders in hypothyroidism are significantly attributable to insulin resistance and vitamin D deficiency. In the present study we tried to establish any interrelationship between Increased insulin resistance and decreased vitamin D levels in hypothyroid patients along with their dependence on the thyroid index parameters. Methods: In a hospital based case control study including 54 hypothyroid cases and 100 controls, serum fT4, TSH, 25 OH vitamin D and HOMA-IR were measured using ELISA. Data were analyzed for difference of mean values between case and control groups. Correlation and regression analyses were done to find out the strength of association and dependence of HOMA-IR and vitamin D with other study variables. Results: Vitamin D was significantly reduced and HOMA-IR was significantly elevated in the case group. Although vitamin D and HOMA-IR showed significant negative and positive correlations respectively with TSH, they did not show any such significant dependence on TSH in the multiple linear regression analysis (β = -.197 and .087, P = .082 and .465 respectively). Vitamin D levels showed significant dependence on fT4 level and the HOMA-IR index (β = .293 and -.372, P = .021 and .004 respectively) while HOMA-IR index showed such dependence on the thyroxine level and vitamin D level (β = -.270 and -.404, P = .042 and .004 respectively). Conclusion: A compromised status of both vitamin D homoeostasis and increased insulin resistance not only exist side by side in hypothyroid patients but they significantly potentiate each other in a linear manner.
