Investigation of GLP1 and gip levels change in patients with hyperthyroidism before and after treatment

The phenomenon that orally administered glucose results in a more prominent insulin response than the equivalent amount of intravenous glucose stimulating the same level of increase in blood glucose is called the incretin effect. Lack of incretin effect causes relative insulin deficiency and hyperglycemia. The main hormones responsible for the incretin effect are GIP and GLP1. Thyroid hormones (T4 and T3) accelerate the absorption of glucose from the intestine, increase the release of glucose from glycogen stores and affect the hepatic demolition of insulin. Development of glucose intolerance and hyperglycemia in patients with hyperthyroidism may be due to the negative effects of incretin levels. Starting from that point, we aimed to assess incretin levels and incretin levels change with hyperthyroidism treatment in patients with hyperthyroidism. 24 persons were enrolled in the study. 12 of them were hyperthyroidism group and the other 12 were healthy control group and they were compared. Besides, tests were repeated after providing euthyroidism in patients with hyperthyroidism and these results were also compared. Oral glucose tolerance test was performed in patients with 75 g glucose. GLP1 and GIP levels were measured at 0, 30, 60, 90, and 120 minute. There was no statistically significant difference between groups in terms of temporal GLP1 and GIP response for oral glucose load. Peak GLP1 level was reached at 60 minutes and GIP was at 90 minutes in both groups. Areas under the curve (AUC) of incretin levels of hyperthyroidism and control groups were compared and statistically significant difference was not seen between groups in terms of AUCs of GLP1 and GIP. GLP1 and GIP measurements did not change before and after the treatment in the hyperthyroidism group. Peak GLP1 level was reached at 60 minutes in hyperthyroidism group before the treatment but it was reached at 30 minutes after providing euthyroidism. Peak GIP1 level was reached at 90 minutes in hyperthyroidism group before the treatment but it was reached at 60 minutes after providing euthyroidism. AUCs of incretin levels before and after providing euthyroidism were compared and it was seen that AUCs of GLP1 and GIP did not change after providing euthyroidism. These findings suggest that incretin response for oral glucose load in patients with hyperthyroidism might be preserved. However, as it is known, intestinal transit time is accelerated in hyperthyroidism and this affects the release of GLP1 and GIP. In our study, it was not possible to standardize these conditions in patients. Furthermore, it will be difficult to adapt the results to the general population because of the limited number of patients in our study. Our study will be a guide for studies involving larger and more homogeneous groups of patients, because it is the first study done on this subject