Circadian rhythm of testosterone and prolactin in the ageing

The role which testicular hormones have on the decrease of sexual function in ageing men is still uncertain, but of primary interest. Previously, it has been known that the impairment of Leydig cell activity is a causal factor in the decreasing sexual function in ageing men. The present study is an evaluation of some chronobiological aspects, which directly or indirectly concern the 'Gonadostat' in ageing men, in order to determine of any change of the hypothalamic-pituitary axis occurs during the ageing process. The results from a group of 18 young men aged between 21 and 37 were compared with the results from a group of 28 older men between the ages of 67 and 98. The daily variations of testosterone (T) levels were determined in both groups of men as its circadian rhythm is well known in adult men. Moreover, the nocturnal secretory pattern of prolactin (PRL) was studied in 6 of the 28 elderly men. When comparing the usual increase of T levels in adult men, which occurs in the morning, there were no significant differences found in the older group of men between early morning and evening. The PRL levels showed no nocturnal increase in 4 of the 6 men. A hormonal impairment in the central nervous system may, in fact, be associated with the testicular deficiency leading to the decrease in sexual function of ageing men.