Catabolic steroids, also known as corticosteroids, mimic the function of cortisol. Produced by the adrenal glands, one of the main functions of cortisol is to control the body's immune response. Sometimes, insufficient amounts of the hormone are produced, or the immune system requires a higher level of control. In these instances, catabolic therapies enhance natural cortisol production. Available in tablets, injections, creams, and as a component in inhalers, catabolic steroids mainly reduce inflammation and suppress the immune system, and can also function as replacement therapy when the body produces insufficient amounts of cortisol.
This treatment reduces inflammation by limiting the inflammatory response of the immune system. When there is infection present, the immune system sends out inflammatory cells to surround the source of the infection to keep it localized and prevent it from spreading to the rest of the body. The steroids inhibit the production of inflammatory cells, such as lymphocytes, and products of inflammation, including prostaglandins and leukotrines. Blood vessels also become constricted, minimizing the onslaught of inflammatory cells. Some allergic reactions and a number of inflammatory conditions are treated in this way, including asthma, arthritis, and chronic obstructive pulmonary disease (COPD).
Immunosuppression is also achieved by the use of catabolic steroids. They are commonly prescribed for autoimmune diseases, where the immune system perceives its own tissue as a foreign invader and chronically attacks it. Steroids decrease both the number of lymphocytes that are produced by the immune system and the extent of their function, resulting in a significant reduction of the attack on healthy cells. The steroids suppress the immune system in a number of autoimmune diseases, including rheumatoid arthritis, lupus, and inflammatory bowel diseases such as ulcerative colitis and Crohn's disease. Due to the immune system being depressed by the catabolic steroids, an unwanted side effect of the therapy is that patients are much more susceptible to infection.
Finally, doctors use catabolic steroids for replacement therapy in patients who do not naturally produce sufficient amounts of cortisol, which subsequently affects their bodies' metabolisms. Insufficiency may be due to the adrenal glands not being properly formed, glands that have been impaired, for example, by medication, and glands that have been damaged. In Addison's disease, for example, the adrenal glands can become injured by the person's own immune system. As a result, the glands do not produce an adequate amount of cortisol and require replacement therapy with catabolic steroids.