Abstract
Male hypogonadism, or testosterone deficiency syndrome (TDS), results from a failure of the testes to produce adequate androgen. Patients have low circulating testosterone in combination with clinical symptoms such as fatigue, erectile dysfunction, and body composition changes. The cause may be primary (genetic anomaly, Klinefelter's syndrome) or secondary (defect in hypothalamus or pituitary), but often presents with the same symptomatology. In the older patient, androgen deficiency of the aging male (ADAM) is an important cause of secondary hypogonadism because testosterone levels decline progressively after age 40. Hypogonadal patients have alterations not only in sexual function and body composition, but also in cognition and metabolism. Regardless of etiology, hypogonadal patients who are both symptomatic and who have clinically significant alterations in laboratory values are candidates for treatment. The goal of hormone replacement therapy in these men is to restore hormone levels to the normal range and to alleviate symptoms suggestive of hormone deficiency. This can be accomplished in a variety of ways, although most commonly testosterone replacement therapy (TRT) is employed.