Insulin release and carbohydrate tolerance in hyperthyroid patients during non-selective or selective...

The insulin release and the glucose disappearance rate (K-value) during an iv glucose tolerance test were evaluated in 20 hyperthyroid patients before and during treatment with either a non-selective (propranolol, n = 10) or a selective (metoprolol, n = 10) beta-1-adrenoceptor blocking agent. Mean daily doses were 240 mg of propranolol and 280 mg of metoprolol, administered four times daily for 10 to 14 days. The insulin increase after glucose injection remained unchanged during treatment with each drug. Fasting blood glucose concentrations and the K-values were not altered during treatment. Sixteen patients were re-investigated 10 to 36 weeks later when euthyroid due to treatment by surgery, thyrostatic drugs or radioiodine. In the euthyroid state mean serum insulin concentrations after the glucose load were not significantly different from the values found when the patients were hyperthyroid. However, mean fasting blood glucose concentrations decreased from 5.5 mmol/l to 5.0 (P less than 0.01) and the mean K-value increased from 1.5 to 2.0 (P less than 0.05) when the patients were euthyroid. It is concluded that short-term treatment of hyperthyroid patients with non-selective or selective beta-1-adrenoceptor blocking agents does not impair the glucose stimulated insulin secretion or the carbohydrate tolerance.