Steroids are a class of compounds that share a similar chemical structure. This broad group of chemicals includes many normal substances in the body (such as cholesterol), vitamins (vitamin D), hormones (for example, the sex hormones and their derivatives), and drugs given to treat inflammation (hydrocortisone, prednisone). The adrenal glands secrete a number of steroid hormones, known as corticosteroids, that are important for the maintenance of blood pressure, blood glucose levels, salt and water balance, and other critical body processes. However, when we speak of steroid abuse by athletes, doctors are referring to the misuse of the so-called "anabolic steroids," which are manufactured drugs similar to the male sex hormone testosterone.
The term anabolic refers to the muscle-building properties of these man-made substances. Available legally only by prescription, anabolic steroids are sometimes prescribed by doctors to treat conditions in which testosterone levels are abnormally low, or in certain chronic conditions such as AIDS that are associated with loss of muscle mass. Athletes, bodybuilders, and other people sometimes abuse anabolic steroids in order to improve performance and physical appearance.