Stimulation tests of human growth hormone secretion by insulin, lysine vasopressin, pyrogen and glucagon

Firstly, comparisons have been made of the secretion of human growth hormone (HGH) that was induced by insulin, lysine vasopressin and pyrogen injections in order to study whether these substances can be utilized as a rapid test of HGH secretion. In insulin test, a fall of the fasting blood glucose level by 28.6% or more seemed to be sufficient to provoke adequate HGH elevation, and 9.4 ng/ml or higher HGH increment was recognized as being normal, because lysine vasopressin and pyrogen produce varying degrees of side-effects and are less specific and unpredictable in the release of HGH. Secondly, the pharmacologic effects and mechanism of action of exogenous glucagon upon the HGH secretion were studied. In normal subjects after one mg sc glucagon, there was a mean peak blood glucose level of 142. 4±3.l mg/lOO ml at 30 min, HGH levels reached a mean peak level of 22. 6±4. 8 ng/ml at 150 min, and no false negative response was noted. In patients with hypopituitarism, there was no positive response in plasma HGH levels after the sc glucagon. The present study revealed that the rise and subsequent fall of blood glucose are not the sole mechanism responsible for the effct of glucagon on HGH secretion, and that the HGH secretion in response to the sc glucagon was not triggered by cathecholamine via the stimulation of the adrenal medulla.