Growth hormone and the steroid binding β-globulin of human plasma

Abstract

The possible influence of growth hormone on the binding activity of the steroid-binding β-globulin (SBβG) in human plasma has been studied. Growth hormone has a chronic effect on SBβG binding. Acromegalic patients with evolutive disease have an SBβG activity about 40% lower than normal. Daily intramuscular injections of 5 mg human growth hormone in 5 growth-retarded children did, after 2–3 days, depress SBβG activity to about three-quarters of the original value. Other experiments give the impression that growth hormone also has an acute effect on SBβG binding. Indeed, significant but short-lived decreases in SBβG activity are noted 2–3 h after the beginning of sleep and these decreases correlate significantly with increases in serum growth hormone levels. Similar decreases are found 30 min after the end of a short period of violent exercise or 30–90 min after an arginine infusion. But, after intravenous injection of insulin or after oral administration of glucose, where changes in growth hormone are also noted, no clearcut variations in SBβG activity occur. Moreover, intramuscular injections of human growth hormone, although inducing marked increases in the immunoassayable growth hormone of serum, do not alter immediately SBβG activity. The decrease in plasma binding after an arginine infusion was paralleled in 4 out of 5 cases by an acute fall in serum testosterone.