Possible role for insulin receptors in the mechanism of thiazide induced glucose tolerance.

The role of cellular insulin receptors in the mechanism of thiazide induced glucose intolerance was studied in 10 non-diabetics and six diet controlled type II diabetics with mild essential hypertension. Glucose tolerance tests (75 g) were performed at the start of the study, after one month of placebo and after one month on bendrofluazide 5 mg daily. Erythrocyte insulin receptor status was measured on each occasion in the fasting state. In non-diabetics, low affinity insulin receptor concentration increased after bendrofluazide but high affinity receptor concentration remained unchanged. In the diabetics, there was no change in either high or low affinity insulin receptor concentration. No change in insulin receptor affinity occurred in either group. In the long term, non-diabetics may maintain normal glucose tolerance on thiazide diuretics by increasing insulin receptor numbers. This adjustment did not occur in diabetic patients which may explain the deterioration in glucose tolerance.