A new look to the andropause: altered function of the gonadotrophs

After being controversial for a long time, the age associated decline in plasma T levels and secretion in normal men is now generally accepted. Although most data point towards a primary testicular origin for the decline in Leydig cell function, other data point towards alterations at the hypothalamo-pituitary levels: T levels in elderly men are decreased notwithstanding an important secretory reserve of both LC and gonadotrophs. Nycthemeral variations in plasma T levels are significantly decreased in elderly men. The increase in immunoreactive LH levels is dysproportionate to the increase of bioactive LH levels. Study of the activity of the LHRH pulse generator in 27 young and 21 elderly men revealed a significant decrease in frequency of high amplitude pulses for both LH and T. Moreover the sensitivity of the gonadostat to sex hormone feed back was significantly greater in the elderly men. Acute administration of an antiopoid (Naloxone), 2 mg i.v. both in young and elderly men at rest showed that in young and elderly men, Naloxone induced a comparable increase of LH levels. Naltrexone on the other hand increased LH pulse frequency in elderly but not in young men. The data show that opioids maintain their inhibitory effect on LHRH secretion in elderly men and suggest either that the opioid tone in the elderly men is decreased or that the response of the gonadotrophs to LHRH is decreased.