A COMPARATIVE STUDY OF SERUM GROWTH HORMONE AND PLASMA CORTISOL LEVELS IN STIMULATION TESTS WITH INSULIN AND PROPRANOLOL-GLUCAGON

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Abstract
Insulin and propranolol-glucagon stimulation tests were carried out on 28 children and 5 adolescents; results of their growth hormone [GH] and plasma cortisol estimations were compared. Subjects (29) with normal GH reserves showed a mean maximum rise of 17.4 .mu.U/ml of serum GH in the insulin test whereas the i.m. injection of glucagon after oral premedication with propranolol produced a rise of 38.5 .mu.U/ml. Five subjects with normal GH reserves showed a reduced hormone output in the insulin stimulation tests but normal response in the propranolol-glucagon stimulation tests. Only 1 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 .mu.U/ml in the insulin and 14.9 .mu.U/ml in the propranolol-glucagon stimulation tests, respectively. Both methods were suitable for studying the pituitary-adrenocortical interrelationships. The mechanism of the release of glucagon-induced GH was not clear but the fall in blood glucose did not seem to play a major role in the process. A stress-like mechanism was equally unlikely because autonomic symptoms occurred only in a small number of subjects after i.m. glucagon administration. Glucagon may possess a releasing-like mechanism which operates in the pituitary itself.