Hyperinsulinemia and insulin resistance is associated with low T3/T4 ratio in pre diabetic euthyroid pakistani subjects

Objective: To investigate the relationship of thyroid hormones in glucose homeostasis in impaired glucose-tolerant subjects with normal thyroid functions. Methods: Cross-sectional analysis was carried out in (n = 260) impaired glucose-tolerant (IGT) and normal glucose-tolerant (NGT) subjects. Thyrotropin (TSH), total triiodothyronine (TT3), total thyroxin (TT4) free T-3 (fT(3)), free T-4 (fT(4)), and insulin were assessed by enzyme-linked immunoassays (ELISA). Fasting plasma glucose (FPG) and HbA1c were measured by glucose oxidase and low-pressure cation exchange chromatography. Homeostasis model of assessment (HOMA-IR) was employed to assess the level of insulin resistance; fT(3)/fT(4) ratio was calculated. Anthropometric measurement and habits were recorded. Results: Marked hyperinsulinemia and insulin resistance were observed in IGT subjects. Serum TT3 and fT(3) levels were significantly low in the IGT as compared to normal glucose-tolerant (NGT) controls. TT4 and TSH were higher in IGT subjects as compared to control subjects. There was a significant positive correlation of TSH with BMI only in the control group (r = 0.351; P<0.05). Correlation of insulin with TT3, fT(3),and TSH was significant (P<0.05) in IGT subjects. A significant low fT(3)/fT(4) ratio was observed in IGT subjects as compared to NGT subjects (P<0.01). In multiple regression analysis, TSH, TT4 and fT(3) contributed significantly to the variance of fasting insulin and insulin resistance in IGT subjects. Conclusion: Hyperinsulinemia and insulin resistance are associated with low T-3/T-4 ratio in pre-diabetic euthyroid Pakistani subjects. (C) 2012 Elsevier Inc. All rights reserved.