What happens to testosterone levels with age?

Testosterone levels generally peak during adolescence and early adulthood. As you age, your testosterone level gradually declines — typically about 1% a year after age 30 or 40. For older men, it's important to determine if a low testosterone level is due to normal aging or if it is due to a disease (hypogonadism).

Hypogonadism hampers the ability to produce normal amounts of testosterone due to a problem with the testicles or with the pituitary gland that controls the testicles. Testosterone replacement therapy, in the form of injections, pellets, patches or gels, can improve the signs and symptoms of low testosterone in these men.