Circadian rhythm of immunoreactive insulin under glycemic stimulus

Abstract

Abstract Five diabetic non‐obese males, non‐insulin dependent, and five healthy subjects were given three constant glucose loads (50 g per os) at the same intervals (08.00 hr; 16.00 hr; 00.00 hr). Blood glucose and plasma immunoreactive insulin (IRI) were measured before and 1 hr after the glucose loads. The test was repeated three days later, with varied glucose loads sequence: the 1st glucose load was given at 16.00 hr. In the controls the net increase of blood glucose was less in the morning than in the afternoon and at night. The insulin response to oral glucose exhibits a cyclic pattern with a peak in the morning, which was unaltered by prolonging the period of caloric deprivation. In the diabetics both basal values and the net increases of blood glucose (AG) were higher in the morning, decreasing in the afternoon and reaching the trough during the night. No clear pattern of cyclicity could be demonstrated in respect of insulin response to glucose.