Testosterone is a male hormone and is defined as the most potent of the natural androgens. These androgens usually cause the male sexual characteristics to develop. They include a beard, deep voice, and strong muscles. This natural hormone continues in life to provide sex drive, keep muscles strong and other important male functions.As the name indicates, Testosterone is a sex hormone that is found inside the testicles. However, there are also small amounts of testosterone that are produced in the woman's ovaries as well as in adrenal system. Testosterone medication belongs to a class called androgens and anabolic steroids. It is given as an injection in the treatment of a number of conditions that are a result of lack of this hormone in the bodies. Therefore, Testosterone is prescribed for indications such as impotence, delayed puberty, and other hormonal imbalances. Testosterone is also given as an injection in the treatment of breast cancer, particularly that which has already spread to other body parts (metastatic breast cancer).