Testosterone replacement therapy is a treatment for men that suffer from hypogonadism. As men age, their testosterone levels begin to dwindle which can cause problems such as depression, erectile dysfunction, and loss of energy. Testosterone replacement therapy, also known as androgen replacement therapy, is when a health professional replaces or adds to the testosterone that is available in a person’s body. Testosterone can be added by way of injections, pills, patches, gels, and even pellets that are implanted under the skin. The end result of testosterone replacement therapy is to replace the level of testosterone that was lost and regain optimum health.