The Effect of Hypothyroidism on Insulin Sensitivity and Their Influence on the Serum Lipid Profile and Renal Function

The overt and subclinical hypothyroidism is more prevalent in patients with diabetes mellitus than in general population. Recently, more studies have been warranted to elucidate the relationship between thyroid hormones disorders and the insulin activity. The present study aims to investigate the correlations between the thyroid hormone levels in subclinical and overt hypothyroid patients with the insulin resistance and their impact on serum lipid profiles and kidney function. Methods: A total of fifty newly diagnosed hypothyroid patients were recruited for the study and classified into: 1) Subclinical hypothyroid (SH) group: n-26; 2) Overt hypothyroid (OH) group: n=24, and control (C) group: n=18. Fasting blood was collected and serum was used for biochemical analysis. Results: The fasting serum insulin, glucose levels and the estimated insulin resistance index (HOMA) of the SH and OH groups were significantly (P<0.001) elevated compared to control. The regression analysis reviled a significant negative correlation between FT4 and insulin (r=-0.32, P=0.04) and significant positive correlations between TSH and insulin (r=0.57, P=0.002), between TSH and HOMA (r=0.51, P=0.001), between HOMA and uric acid (r=0.37, P=0.02), and between TSH and TG (r=0.47, P=0.002). The serum creatinine, urea and uric acid concentrations were significantly (P<0.001) elevated in the OH group but not the SH. The serum total cholesterol, TG and LDL-cholesterol were significantly elevated in both SH and OH. Conclusion: Hypothyroidism is associated with insulin resistance, renal impairment, hyperurecemia and dyslipidemia, which are atherosclerotic risk indicators. The TSH had maximum impact on the changes. Subclinical and overt hypothyroid patients with elevated TSH are at high risk of developing atherosclerosis, thus may need close monitor to contain the rise in plasma TSH.