Introduction

Testosterone levels diminish with age, as both testosterone production and metabolic clearance decrease. These hormonal alterations lead to loss of libido, decreased muscle strength, alterations in memory, diminished energy and well-being, and possibly osteoporosis. Testosterone appears to influence the frequency of nocturnal erections; however, low testosterone levels do not affect erections produced by erotic stimuli. Indeed, few if any definitive signs or symptoms of androgen deficiency may be apparent in men, in contrast to those seen in women at menopause, when female sex hormone levels fall.

Aging, rather than androgen deficiency per se, is associated with a diminution of sperm quality and quantity, although spermatogenesis does not completely cease.