Effects of glucocorticoids on pituitary hormonal responses to hypoglycemia. Inhibition of prolactin release.
The characteristics of pituitary hormonal responses to insulin-induced hypoglycemia were investigated in 16 normal men. In all subjects, levels of blood sugar fell below 35 mg/100 ml. A statistically significant increase in mean plasma levels of prolactin, ACTH, cortisol and growth hormone was observed. Prolactin levels increased in all subjects but one; individual peak values were 1.4 minus 8.4 times greater than base levels. The kinetics of prolactin, GH and ACTH responses were similar; in particular, the onset of release (25 min) of prolactin, GH and ACTH was similar. After dexamethasone administration, insulin tolerance tests wererepeated in a number of subjects using adequate amounts of insulin to achieve hypoglycemia equivalent to that obtained in the control experiments. The administration of 1 mg of dexamethasone the evening before the test suppressed basal levels of ACTH and cortisol and the ACTH-but not the cortisol-response to hypoglycemia. Both basal levels of prolactin and prolactin response to hypoglycemia were significantly lowered but growth hormone response was not modified by administration of 1 mg of dexamethasone. The administration of larger doses of dexamethasone (1 mg every 6 h for 2 days) almost completely suppressed basal levels of ACTH, cortisol and prolactin, as well as the hypoglycemia-induced release of these hormones. In contrast, the growth hormone response to hypoglycemia was only partially inhibited. These findings demonstrate that both basal secretion and hypoglycemia-induced release of prolactin, ACTH, cortisol and growth hormone are suppressible by glucocorticoids.
D000293:Adolescent; D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000328:Adult; D001786:Blood Glucose; D003907:Dexamethasone / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007328:Insulin; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000378:metabolism*; D013268:Stimulation, Chemical; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D013006:Growth Hormone; D006854:Hydrocortisone