Effect of exogenous growth hormone administration on endogenous growth hormone secretion induced by a met-enkephalin analog.
Exogenous growth hormone (hGH) administration in humans attenuates the endogenous growth hormone (GH) response to some pharmacological stimuli; in particular, pretreatment with hGH completely blocks the serum GH response to growth hormone-releasing hormone. In order to evaluate the mechanism(s) whereby opiods induce GH secretion in man, we gave the following treatments to six healthy male volunteers: (a) IV saline; (b) a met-enkephalin analog G-DAMME 250 micrograms IV as a bolus at time 0'; (c) hGH 2 IU as an IV bolus at time -180'; (d) G-DAMME as above, preceded by hGH as above. In our study, G-DAMME stimulated GH secretion both basally (peak 17.9 +/- 6.0 ng/ml) and, to a lesser extent, after hGH pretreatment (6.0 +/- 2.7 ng/ml). Since in our study G-DAMME was able to partially overcome the inhibitory effect of hGH administration, it is suggested that opioids act through an inhibition of somatostatin release and not through a GHRH-dependent pathway. However, an additional direct effect of hGH on pituitary somatotrophes cannot be excluded.
Fanciulli
G
G
Chair of Endocrinology, University of Sassari, Italy.
Oliva
O
O
Tomasi
P A
PA
Pala
A
A
Bertoncelli
A
A
Dettori
A
A
Delitala
G
G
D000328:Adult; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000494:pharmacology*; D013006:Growth Hormone / Q000378:metabolism* / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D012016:Reference Values; D016037:Single-Blind Method; D013997:Time Factors
D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D013006:Growth Hormone