Endocrine Abstracts

The main hormones responsible for the incretin effect are GIP and GLP-1. Thyroid hormones accelerate the absorption of glucose from the intestine, increase the release of glucose from glycogen stores and affect the hepatic demolition of insulin. We aimed to assess incretin levels in patients with hyperthyroidism before and after thyroxine therapy. Total 24 subjects (12 hyperthyroid and 12 controls) were enrolled in the study. Oral glucose tolerance test was performed in patients with 75 g glucose. Glucose, insulin, C-peptide, GLP-1 and GIP levels were measured at 0, 30, 60, 90, and 120^th minutes. Tests were repeated after providing euthyroidism in patients with hyperthyroidism. Basal glucose level was higher in hyperthyroidism group when compared control group (P=0.03). There was no statistically significant difference between groups in terms of temporal GLP-1 and GIP response for oral glucose load. Peak GLP-1 level was reached at 60 minutes and GIP was at 90 min in both groups. GLP-1 and GIP measurements did not change before and after the treatment in the hyperthyroidism group. Peak GLP-1 level was reached at 60^th minutes in hyperthyroidism group before the treatment but it was reached at 30^th minutes after providing euthyroidism. Peak GIP-1 level was reached at 90^th minutes in hyperthyroidism group before the treatment but it was reached at 60^th minutes after providing euthyroidism. These findings suggest that total incretin response for oral glucose load in patients with hyperthyroidism might be preserved. However, peak incretin responses are changed after providing euthyroidism.