More than 40 percent of men 45 and older have low testosterone levels. Testosterone is far more than a male sex hormone. There's no question men with extremely low testosterone-also known as hypogonadism-have decreased interest in sex and decreased sexual performance-but low testosterone levels have much broader implications. Testosterone is also important for mood stability, muscle growth, bone density and body fat levels.
Men with untreated hypogonadism tend to be more depressed, angry, and fatigued than their healthy peers. Any man over 40 with symptoms of depression or fatigue-with or without sexual concerns-should get his testosterone level measured. The best time to have this blood test is first thing in the morning. Testosterone in the body can be supplemented though testosterone replacement therapy, in the form of a gel applied daily or an injection every two to four weeks. A new, long-acting injection is awaiting approval in the United States.