Insulin response to tolbutamide-glucose load in normal and diabetic subjects.

Insulin response to the oral administration of 100 g glucose (glucose tolerance test, GTT) did not differ significantly in eight normal subjects from that to GTT with 50 g glucose. Repeated injection of tolbutamide revealed a small rise in plasma insulin in a group of five normal subjects. Insulin response to glucose was delayed and elevated in mild diabetics while that was minimum in moderate and severe diabetic patients. However, there was no significant difference between the insulin response to glucose in normal and diabetic subjects, because of a wide scattering. When 50 g glucose was ingested 60 min after the injection of 1 g tolbutamide (TGTT), insulin response in diabetics rather decreased. Insulin levels 30 min after oral glucose in TGTT was significantly lower in diabetics than in the normal subjects. It was suggested from the present experiment that TGTT provides a discrimination of insulin response in diabetics from that in normal subjects.