Male Reproductive Aging

Abstract As men age, their reproductive functions, both spermatogenesis and testosterone production, diminish, but slowly and to a relatively small degree. The fall in testosterone appears to be the result of primary hypogonadism in some men and secondary hypogonadism, associated with concomitant illness, in others. The fall in testosterone production may have some consequences, including decreased sexual function, energy, mood, muscle mass, and bone density. Increasing the serum testosterone of older men with low testosterone to that of young men does improve sexual function, mood, walking, anemia, and bone density, but not energy or cognitive function. The cardiac and prostate risks of increasing testosterone in older men are not yet known.