Objective: To investigate the existence of an opioid stimulatory tone on growth hormone (GH)
secretion in the human male. Design: Seven healthy male volunteers, aged 19-30, were studied in the Endocrine Unit of
the University of Sassari. GH-releasing hormone (GHRH), 100 µg as an intravenous (IV)
bolus, as administered with and without preadministration of IV naloxone, 2 mg as
a bolus followed by a constant infusion of 2 mg/h. Blood samples were taken for 120
minutes after GHRH administration. Results: Naloxone significantly blunted the GH response to GHRH, measured either as mean peak
value (at times 30 to 90) or as integrated concentrations. Conclusions: Naloxone is able to decrease the effect of a maximal dose of GHRH, thus suggesting
the existence of an opioid stimulatory tone on GH secretion.
Key words
Hypothalamus - Pituitary Gland - GH - Opioids - Naloxone - GHRH
