Androgens and the aging male.

In contrast to women, men do not experience a sudden cessation of gonadal function comparable to menopause. However, there is a progressive reduction in male hypothalamic-pituitary-gonadal (HPG) axis function: testosterone levels decline through both central (pituitary) and peripheral (testicular) mechanisms, and there is a loss of the circadian rhythm of testosterone secretion. The progressive decline in testosterone levels has been demonstrated in both cross-sectional and longitudinal studies, and overall at least 25% of men over age 70 meet laboratory criteria for hypogonadism (ie, testosterone deficiency). Such age-associated HPG hypofunctioning, which has been termed "andropause," is thought to be responsible for a variety of symptoms experienced by elderly men, including weakness, fatigue, reduced muscle and bone mass, impaired hematopoiesis, sexual dysfunction (including erectile dysfunction and loss of libido), and depression. Although, it has been difficult to establish correlations between these symptoms and plasma testosterone levels, there is some evidence that testosterone replacement leads to symptom relief, particularly with respect to muscle strength, bone mineral density, and erectile dysfunction. There is little evidence of a link between the HPG axis hypofunctioning and depressive illness, and exogenous androgens have not been consistently shown to have antidepressant activity. This article reviews the relationship between androgens, depression, and sexual function in aging men.