Diagnostic criteria are based on physical assessment, hormone levels, dynamic testing (GnRH and clomiphene stimulation tests), and semen analysis. Additional diagnostic studies include bone densitometry, pituitary imaging, genetic studies, testicular biopsy, and scrotal exploration.

No studies have clearly indicated that a particular testosterone level is associated with pituitary tumors. However, a total testosterone level of less than 150 mg/dL should trigger a pituitary imaging study, even in the absence of other symptoms, the guidelines state.

The treatment goal is the same in each target population—to restore sexual function (including fertility, if desired and possible), libido, behavior, and physical well-being. In addition to decreased sex drive and sexual activity, men with low testosterone levels may exhibit anger, depression, fatigue, and confusion, as well as physical effects such as decreased muscle mass and bone density and associated osteoporosis.

Based on the results of recent studies, the new guidelines state that testosterone replacement often alleviates associated psychological conditions, increases virilization, and optimizes bone density. Recent studies also indicate that the therapy may normalize growth hormone levels in elderly men. Therapy also may decrease cardiac mortality in this population, but the guidelines make no specific recommendations in this area because the link between cardiovascular disease and low testosterone is not fully understood.

The AACE guidelines evaluate testosterone replacement methods (injection, patch, gel, and oral agents) and stress that patients on testosterone replacement need to be carefully monitored for possible adverse effects. Careful monitoring of prostate-specific antigen is particularly important, and men with known prostate cancer should never use testosterone replacement therapy.