Human pancreatic growth hormone releasing factor (hpGRF): GRF- and GH-levels after bolus injection and infusion of hpGRF.

Abstract

Synthetic human pancreatic growth hormone releasing factor (hpGRF) was given as an i.v. bolus to healthy volunteers in 5 different dosages (3.3 micrograms to 200 micrograms hpGRF). In addition 11 healthy subjects were infused over 2 respectively 5 hours in a dosage of 100 micrograms hpGRF/h after receiving a bolus of 50 micrograms hpGRF. Four healthy subjects served as placebo controls. GH, PRL, TSH, and GRF were measured by specific radioimmunoassays. The results show the clearcut dose response relationship between the administered GRF dosage and the resulting GH response from 3.3 to 50 micrograms hpGRF i.v. Higher dosages of hpGRF did not lead to a more pronounced GH response though there was a linear dose response relationship between the administered hpGRF and the GRF immunoreactivity 5 minutes after injection. Infusion of hpGRF could not sustain elevated GRF levels and a second bolus of 50 micrograms hpGRF given at the end of the 2-respectively 5-hour infusion led to a minor increase compared to the first bolus. 100 micrograms hpGRF was given to 14 patients with active acromegaly leading to a significant rise of the GH levels with the exception of 3 patients. Of the latter 3 two had received previous therapy, and one patient suffered from ectopic GRF hypersecretion. When GH responses to hpGRF were compared to the responses to other releasing hormones there was no correlation. After transsphenoidal surgery divergent responses of GH were seen. In one patient with low basal GH and an exaggerated rise after GRF before surgery there was no response after successful transsphenoidal operation.(ABSTRACT TRUNCATED AT 250 WORDS)