A comparative study of serum growth hormone and plasma cortisol levels in stimulation tests with insulin and propranolol-glucagon

Abstract

Insulin and propranolol-glucagon stimulation tests were carried out on 28 children and 5 adolescents and the results of their growth hormone and plasma cortisol estimations were compared. Twenty-nine subjects with normal growth hormone reserves showed a mean maximum rise of 17.4 muU/ml of serum growth hormone in the insulin test whereas the intramuscular injection of glucagon after oral premedication with propranolol produced a rise of 38.5 muU/ml. Five subjects with normal growth hormone reserves showed a reduced hormone output in the insulin stimulation tests but normal response in the propranolol-glucagon stimulation tests. Only one subject showed a poor response in the propranolol-glucagon but normal response in the insulin stimulation test. In 30 subjects with normal adrenocortical function the mean maximum increase of plasma cortisol was 15.6 muU/ml in the insulin - and 14.9 muU/ml in the propranolol-glucagon stimulation tests, respectively. Both methods are suitable for studying the pituitary-adrenocortical interrelationships. The mechanism of the release of glucagon-induced growth hormone is not clear but the fall in blood glucose does not seem to play a major role in the process. A stress-like mechanism is equally unlikely because vegetative symptoms occurred only i a small number of subjects after intramuscular glucagon administration. It is possible that glucagon possesses a releasing-like mechanism which operates in the pituitary itself.