A DIVERGENCE OF PLASMA GROWTH HORMONE RESPONSE BETWEEN GROWTH HORMONE-RELEASING FACTOR AND INSULIN-INDUCED HYPOGLYCAEMIA AMONG MIDDLE-AGED HEALTHY MALE SUBJECTS

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Abstract
The capability of the anterior pituitary gland to secrete GH in response to an intravenous injection of growth hormone-releasing factor (GRF) and insulin-induced hypoglycaemia was evaluated in 9 healthy male subjects ranging in age between 37 and 52 years old. Plasma GH response to 100 .mu.g human GRF showed considerable intersubject variation and the increment of the peak value from the basal did not exceed 5 ng/ml in four out of 9 subjects. In contrast, insulin-induced hypoglycaemia resulted in a consistent stimulation of GH that exceeded 21 ng/ml in all subjects. The mean peak GH response after insulin-induced hypoglycaemia was significantly higher than that after GRF (27.4 .+-. 1.6 vs 10.6 .+-. 1.9 ng/ml). These results demonstrate that a significant divergence exists in plasma GH responses between the two provocative tests in the middle-aged subjects and suggest that the stimulation of GH following insulin-induced hypoglycaemia is not mediated solely by endogenous GRF.