Androgen replacement therapy

Androgen replacement therapy is hormone treatment for middle-aged and older men which is often intended to counter the natural effects of aging. Androgen replacement is also used for men who have lost their testicular function to disease, or cancer, or to other causes.

As men enter middle age they may notice changes caused by a relative decline in testosterone: fewer erections, fatigue, thinning skin, declining muscle mass and strength, more body fat. This dissatifaction with the changes of aging has led to the development of the idea of androgen replacement therapy.

Male hormones are called androgens from Greek words andro meaning man, and gen meaning giving birth to. Primary among them is the natural hormone testosterone, which is produced in the testes, ovaries and adrenals. Females also produce testosterone in the adrenals and as a precursor to estrogen, but the amount of circulating testosterone is generally far less than in males, although the ranges on the two genders overlap. Both sexes also produce an androgen precursor called dihydroepiandrostene (DHEAS) from which the body can make androgens. Androgens cause the secondary sex characteristics of males: facial hair, thicker skin, low body fat, deeper voice, muscularity, penis and scrotal growth and darkening, broad shoulders, body hair, erection of the penis, etc. With increasing age, testosterone production declines, and many of these changes start to reverse.

This "decline of maleness" with age has given rise to a term: "andropause". This term implies a parallel with menopause in women, although the two states are by no means equivalent. The term manopause has also been used in the popular press.

There are several artificial androgens, including nandrolone and various other manipulations of the testosterone molecule. Androgen replacement is via patch, tablet, pill or cream; or depot injections given into fat or muscle.

Users report an increased alertness and well-being, heightened libido and erection ability, increase in lean muscle mass and concomitant decrease in body fat.

There is the possibility of abuse: some athletes may demand far higher levels of androgen than normal in order to out-perform others, other people may feel they require greater doses in order to achieve what they perceive as a feeling of greater well-being.

Therapeutic indications
Androgen replacement has a direct role in the treatment of hypogonadism, and may improve associated features such as anemia, and fatigue.

In additon, a number of other effects of testosterone have led to research into possible therapeutic roles in:
 * erectile dysfunction
 * osteoporosis
 * diabetes mellitus
 * chronic heart failure
 * dementia, but the evidence base is small and the balance of benefit needs to be clarified