THE EFFECT OF A MET-ENKEPHALIN ANALOG ON GROWTH-HORMONE, PROLACTIN, GONADOTROPINS, CORTISOL AND THYROID STIMULATING HORMONE IN HEALTHY ELDERLY MEN

The aim of the study was to evaluate the effect of the guanyl derivative of the opioid analogue D-ala2,MePhe4-Met-enkephalin-(o)-ol (G-DAMME) on pituitary secretion in healthy elderly men. Nine healthy elderly men (65-88 years) and 10 young adults (20-30 years) were studied. GH, PRL, gonadotropins, cortisol (to evaluate the effect on ACTH) and TSH were measured after G-DAMME (0.2 5 mg iv) or placebo administration. In elderly men, the GH response to G-DAMME was reduced or absent, while prompt GH release was found in all young men. G-DAMME lowered LH levels in young men but not in elderly men. No significant variations in FSH levels after G-DAMME and placebo were noted in either group of subjects. A similar and significant rise in PRL and TSH, and a fall in cortisol, after G-DAMME was observed in both elderly and young adults. We have demonstrated that the sensitivity to opioid modulation by G-DAMME on PRL, TSH and cortisol secretion is unchanged with aging. On the other hand, the data indicate that LH and GH responsiveness to G-DAMME change with age.