Objective: To investigate the relationship of thyroid hormones and insulin secretions in glucose homeostasis in impaired glucose tolerant and type 2 diabetic subjects, with normal thyroid functions.
Methods: Retrospective cross sectional analysis was carried out on (n=266) impaired glucose tolerant, type 2 diabetics and normal glucose tolerant subjects. Thyrotropin (TSH), total triiodothyronine (TT3), total thyroxin (TT4) and insulin were assessed by enzyme linked immunoassays (ELISA). Insulin and TSH were assessed by Immunoenzymometric Assay (Type 3), while TT3 and TT4 were assessed by competitive enzyme immunoassay (type 5). Fasting plasma glucose 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. Anthropometric measurement and habits were recorded.
Results: Serum TT3 levels were significantly lower in the IGT and diabetics as compared to normal glucose tolerants (controls). TT4 and TSH were higher in IGT subjects as compared to control and diabetics. IGT subjects were more hyperinsulinemic and insulin resistant as compared to diabetics. There was a significant positive correlation of TSH with BMI only in control group (r=0.351; P<0.05). TT3 had significant and positive correlation with TT4 (r=0.700, r=0.577) in control and diabetic respectively (P<0.01). Correlation of insulin with TSH was significant (r=−0.457) in IGT subjects. In multiple regression analysis TSH, TT4 contributed significantly to the variance of fasting insulin in IGT subjects. Pathophysiology of chronic hyperglycemia and persistent insulin resistance suppressed the true picture of thyroid hormone status in diabetic subjects.
Conclusion: T4 and TSH are associated with insulin secretions in IGT subjects. Impaired glucose tolerant subjects can be targeted for better therapeutic options.
The study was approved by ethical committee of the hospital.
25 - 29 Apr 2009
European Society of Endocrinology