The Acute Effect of the Human Growth Hormone under Hyperglycemic Conditions in Man

Abstract

This investigation was performed to evaluate the effect in man of the administration of the human growth hormone (HGH) on the levels of blood sugar, serum insulin (IRI), C-peptide (CPR), glucagon (IRG) and free fatty acids (FFA) under hyperglycemic conditions induced by an intravenous glucose infusion.
Twelve healthy, non-obese, and non-diabetic male volunteers, aged 20-24 years, were selected for the investigation. The studies were begun at 8 a.m. after an overnight fast with the subjects in a recumbent position after 30 min of rest.
In the first series of experiments, glucose was infused intravenously at a rate of 14 mg/ kg/min for 180 min in all subjects as the control experiments. In the second series of experiments, HGH (by Raben) at a dose of 1 mg was given according to the following two procedures : Group A : HGH was administered to 8 subjects by a single intravenous injection within 40 min 10 seconds after initiation of the glucose infusion. Group B : HGH in 250 ml physiological saline was given to 4 subjects by a constant intravenous infusion for 30 min, starting 40 min after initiation of the glucose infusion. Blood samples were taken from the antecubital vein at the opposite side of the glucose infusion before and every 10 min after initiation of the glucose infusion.
The results were as follows :
1) In the first series of experiments, the concentration of blood sugar gradually decreased about 60 min after initiation of the glucose infusion, but the so-called “secondary rise” of HGH was not observed during the glucose infusion.
2) The insulin release induced by the glucose infusion was inhibited by the administration of HGH, which continued for 110 min in Group A and 40 min in Group B.
3) In Group A, the concentration of CPR increased 90 min after the administration of HGH but did not increase in Group B.
4) The concentrations of IRG and FFA did not change after the administration of HGH under such a hyperglycemic condition.
These results clearly demonstrated that acute intravenous administration of HGH caused a decrease in IRI release in hyperglycemic subjects. This indicates that HGH manifests a diabetogenic activity even under hyperglycemic conditions. Further investigation should be necessary to elucidate the mechanism of action of HGH.