Fanciulli G, Oliva O, Tomasi PA. Pala A. Bertoncelli A, Dettori A, Delitala G. Effect of exogenous growth hormone administration on endogenous growth hormone secretion induced by a met-enkephalin analog. Eur J Endocrinol 1996:134:73–6. ISSN 0804–4643
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 opioids 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 μg IV as a bolus at time ′: (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.
Giuseppe Delitala, Chair of Endocrinology, Viale S. Pietro 12, University of Sassari, 07100 Sassari. Italy
