Endocrine Abstracts

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.