Further Studies on Leydig Cell Function in Old Age

Pathophysiological mechanisms leading to a decreased Leydig cell function in old males were studied. Increased basal plasma LH and FSH levels, an increased pituitary reaction to LHRH 200 μg iv, and a decreased responsiveness of the Leydig cells to hCG stimulation, lead to the conclusion that the decreased Leydig cell function in old age has a primary testicular origin. The plasma estrone and estradiol levels are slightly but significantly increased in elderly males, the free estradiol concentration is however unchanged. There exists a highly significant correlation between the (log transformed) apparent free testosterone concentration and LH and FSH levels suggesting that the feedback of the gonadotropin secretion is regulated via the free rather than via total testosterone levels.