Growth hormone and cortisol secretion after propranolol-glucagon testing in the adult

Abstract

Pituitary HGH response to propranolol-glucagon stimulation in a group of obese subjects (n = 45), patients with primary hypothyroidism (n = 13), and patients with hypopituitarism (n = 15) was compared to the response observed in normal subjects (n = 40). In normal and obese subjects, the magnitude of the HGH response to the same stimulus was compared with the results obtained with the insulin tolerance test. In addition, the cortisol response to propranolol-glucagon stimulation in normal subjects (n = 19) was compared to that obtained after insulin hypoglycemia. In the group of normal subjects, a positive HGH response after the propranolol-glucagon test (i.e., a peak value ≥ 9 ng/ml) was found in 38 of the 40 subjects tested. The mean HGH peak value (24.5 ± 2.1 ng/ml) was significantly lower than that (41.1 ± 2.8 ng/ml) on insulin testing ( p < 0.001). In 45 overtly obese subjects, a mean peak value of 11.0 ± 1.3 ng/ml was reached, a significantly blunted response as compared to the group of normal subjects ( p < 0.001). Again the HGH peak after propranolol-glucagon stimulation was significantly lower than the mean HGH response on insulin testing (18.7 ± 1.6 ng/ml) in a comparable group of obese individuals ( p < 0.0025). A consistently blunted HGH response was observed in all the patients with pituitary insufficiency and in ten out of 13 patients with unsubstituted primary myxedema. The increase in plasma cortisol levels after propranolol-glucagon stimulation in normal subjects was comparable to the response after insulin hypoglycemia. It is concluded that the propranolol-glucagon test is a safe and reliable procedure, although normal “nonresponders” do exist, and that it represents a somewhat weaker stimulus for HGH release by the pituitary than postinsulin hypoglycemia. As plasma cortisol levels rise consistently, the test can also be used for the evaluation of the pituitary-adrenal axis.