Changes in the pituitary-testicular axis with age

A large number of endocrinological studies of testicular function in men of different ages suggest that primary testicular failure becomes common and more severe with aging. There is an increasing frequency of impotence, reduced secondary sex hair and testicular atrophy. Serum LH and FSH levels rise, androgen production rates and levels fall and oestrogen levels rise. The clearance of oestradiol falls but the production rate is maintained, in part, through increased peripheral conversion of testosterone to oestradiol. The levels of SHBG rise and free testosterone levels are reduced. Leydig cell responsiveness to hCG is probably reduced but gonadotrope responsiveness to GnRH reasonably maintained in the elderly. There are histological changes in the seminiferous epithelium of old men but these are non-specific. Senescent testicular failure is mainly a primary gonadal disorder but its cause and significance are only poorly understood.