The male population in this country is living longer. An estimated 30 million men in the United States - 12 to 13 percent of the current population - are 65 and older. Over the next few decades, this figure will rise to 60 million, or 25 percent of the population. Longer life often brings decreased testicular function and, accordingly, lower testosterone production.

Numerous studies have shown that blood levels of testosterone decrease in conjunction with the aging process: 8 percent of men have low testosterone when they are in their 40s-60s, 22 percent when in their 60s-80s, and more than 40 percent when they are over 80 years of age.

Symptoms. Aging brings symptoms that include decreased sex drive (libido), depression, loss of stamina, loss of bone density, loss of muscle mass, and a slowing of thought processes. Certainly, there are other potential causes for some of these symptoms, but when they are accompanied by an abnormally low testosterone, this late-onset hypogonadism, currently is referred to as androgen deficiency in the aging male andropause, or ADAM.

Diagnosis. Diagnosis is based on clinical signs and symptoms and blood tests that document low levels of serum testosterone. To distinguish between a primary (testicular) or secondary (pituitary/hypothalamic) cause for the hypogonadism, measurements of serum luteinizing hormone, prolactin, and follicle-stimulating hormone are needed.

Treatment. Treatment is available in injectable, oral and transdermal (skin-patch) form, but oral preparations are least effective and carry a significant risk of liver toxicity. Hormone replacement is recommended only when there is proper laboratory and clinical documentation. Men using testosterone are monitored by their physicians at regular intervals with evaluations that include an assessment of the patient's clinical response, a digital rectal examination, and blood tests for testosterone, hemoglobin and prostate-specific antigen. A lipid profile and liver function test may also be considered.

Benefits of testosterone supplementation may include improvement in any or all of the symptoms described for androgen deficiency in the aging male.