Acute Suppressive Effect of Human Growth Hormone on Basal Insulin Secretion in Man

Abstract

The acute effects of human growth hormone (GH) on the basal levels of glucose and insulin in blood were investigated in 11 healthy men. GH doses of 5, 10, 20, and 40 \g=m\g/kgbody weight were given iv as a constantrate infusion over 30 min, and resulted in peak hormone levels (30 min) of 20.5 \ m=+-\ 1.0, 48.5 \ m=+-\ 2.2, 108.2 \ m=+-\ 4.5, and 229.2 \ m=+-\ 14.6 ng/ml, respectively. There was a small (max 9.8 \ m=+-\2.6 %) but significant decrease in the blood glucose level, observed already at 15 min after the beginning of the GH infusion and persisting up to 90 min. The highest dose of GH induced the most marked changes, but there was otherwise no clear correlation between dose and effect. The basal plasma insulin levels showed a more marked (max 16.0 \ m=+-\ 4.7 %) decrease which was not correlated, in time or in magnitude, with the changes in blood glucose. In some subjects, in whom no significant decrease in blood glucose was observed, plasma insulin still demonstrated a similar fall (max 20.2 \ m=+-\7.6 %). Neither were these changes in plasma insulin correlated to the dose of GH within the range used in this study. The findings suggest that the early, insulin\x=req-\ like effect of GH on blood glucose is distinct from its effect on the pancreas. The latter is a suppressive one, consistent with earlier findings on glucose-induced insulin release.Several studies since the 1930s have established that chronic administration of pharmacological doses of growth hormone (GH) induced a diabetes-like state with hyperglycaemia and hyperinsulinism (Houssay Sc Biasotti 1930;Young 1937; Ikkos Sc Luft 1960;Luft et al. 1969). On the other hand, the acute effect of GH on carbohydrate metabolism has been shown to be an insulin-like one,

Prolonged insulin resistance following insulin-induced hypoglycaemia

“…Growth hormone also has multiple effects on glucose kinetics, varying with the duration of exposure and the time interval after exposure. Several investigators have demonstrated that growth hormone has early insulin-like effects [36][37][38]. However, insulin antagonistic effects of the hormone can be seen 2-12 h after growth hormone administration [39][40][41], and could exert a delayed effect on glucose metabolism since even transient elevations of growth hormone have been shown to impair even transient elevations of growth hormone have been shown to impair glucose tolerance for at least 5 h [41].…”