Effect of propranolol on glucose tolerance in hyperthyroidism.

Glucose tolerance tests were performed on six hyperthyroid patients in the morning and afternoon before, and at the end of treatment with propranolol for 2 weeks. All six subjects showed normal glucose tolerance with a normal diurnal rhythm before treatment and this remained normal in five during treatment with propranolol, while one patient developed abnormal glucose tolerance and the diurnal variation was abolished. No change in insulin levels was noted in any of the patients either before or during treatment. Propranolol may cause deterioration in glucose tolerance in some subjects with hyperthyroidism and this possibility should not be overlooked.