title: Reduction of the effects of growth hormone release inhibiting factor enhances plasma growth hormone response to GHRH.
abstract: Responses of serum growth hormone (hGH) to glucagon (G), growth hormone releasing hormone (GHRH) and G/GHRH were measured in 8 normal adults and 6 patients with growth hormone deficiency (GHD). In normal adults, serum hGH reached its peak value (12.7 +/- 1.6 ng/ml) at 150 +/- 10 min, as blood glucose declined to its minimum after a transitory hyperglycemia in G test. The normal adults were responsive to GHRH test (GH peak 14.7 +/- 2.3 ng/ml at 30 +/- 0 min). In GHD, the responders to both G and GHRH tests showed a strongly positive response in G/GHRH test, with a serum hGH peak value of 34.6 +/- 4.1 ng/ml at 131 +/- 8 min being much higher than that of either single G or GHRH test (P less than 0.01), but without significant difference to the sum of the two single tests (P greater than 0.10). Among GHD patients, only 2 responded to GHRH and G/GHRH tests with hGH peak values 6.8 +/- 0.7 and 6.9 +/- 0.7 ng/ml at 45 +/- 15 and 90 +/- 0 min, respectively, both peak values being essentially similar (P greater than 0.10). We suggest that the mechanism of stimulation of pituitary hGH secretion in G test might involve inhibition of release of hypothalamic GH release inhibiting factor (GHRIF) caused by hypoglycemia after a transitory hyperglycemia following G injection. These results may further confirm our previous postulation (1986) that insulin hypoglycemia may increase hGH release by inhibiting hypothalamic cell secretion of GH release inhibiting factor.
authors.forename: Y F
authors.initials: YF
authors.lastname: Shi
authors.forename: X D
authors.initials: XD
authors.lastname: Fang
mesh_terms: D000328:Adult; D005260:Female; D005934:Glucagon / Q000009:adverse effects / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood* / Q000172:deficiency; D013007:Growth Hormone-Releasing Hormone / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D008297:Male; D013004:Somatostatin / Q000378:metabolism
chemical_list: D013004:Somatostatin; D013006:Growth Hormone; D005934:Glucagon; D013007:Growth Hormone-Releasing Hormone