Androgen deficiency in aging and metabolically challenged men.

Androgen deficiency in aging men is common, and the potential sequelae are numerous. In addition to low libido, erectile dysfunction, decreased bone density, depressed mood, and decline in cognition, studies suggest strong correlations between low testosterone, obesity, and the metabolic syndrome. Because causation and its directionality remain uncertain, the functional and cardiovascular risks associated with androgen deficiency have led to intense investigation of testosterone replacement therapy in older men. Although promising, evidence for definitive benefit or detriment is not conclusive, and treatment of late-onset hypogonadism is complicated.