For women, the loss of androgens (male hormones) begins surprisingly early -- before age 40 -- and results in fatigue, loss of bone mass and decreased sexual desire [source: Boston University School of Medicine]. For men, this gradual change usually peaks at age 50 and ushers in everything from male-pattern baldness to osteoporosis, which is a loss of bone density [source: Shmerling]. A reduction in androgens, which includes testosterone, can have emotional impacts as well. While recent research refutes the fact that male hormones make men act more aggressively, there is one stereotype that seems to hold true: The midlife crisis. About the time a man reaches age 50, he may become bored with his career, marital status or the American dream in general, but this emotional reaction has physiological roots [source: Fisch]. Rather than seeking a boost from a new sports car, most men would be better served by a simple blood test. That's because it can uncover potentially low testosterone levels, which may be the source of depression or dissatisfaction.