Influence of antiopioids on luteinizing hormone pulsatility in aging men.

To investigate whether changes in opioid tone play a role in the age-associated changes in LH release in men, the influence of an antiopioid, naltrexone, on plasma LH levels and LH pulses was studied in a group of young and elderly normal men. The young and elderly men had similar basal LH pulse frequencies, but the frequency of high amplitude (greater than 2 IU/L) LH pulses, mean LH pulse amplitude, maximal LH pulse amplitude and pulse area, were lower in the elderly men. Naltrexone administration (40 mg at 0630 and 2200 h the day before blood sampling and at 0630 h, 30 min before starting frequent blood sampling at 10-min intervals for 12 h) to young men (n = 8) induced a significant increase in individual mean baseline plasma LH levels, LH pulse frequency, and the sum of LH pulse amplitudes. In elderly men (n = 11) only a borderline significant increase in baseline plasma LH levels occurred, and neither LH pulse frequency nor the sum of the amplitudes of LH pulses increased. We suggest that in elderly men either opioid tone or the response of the gonadotrophs to endogenous LHRH is decreased.