A steroid is any of a class of natural or synthetic organic compounds characterized by a molecular structure of 17 carbon atoms arranged around four rings. Steroids are important in biology, chemistry, and medicine. How do corticosteroids work? Corticosteroids help lessen swelling and irritation, called inflammation. The medicine can ease symptoms of inflammatory conditions, such as arthritis, asthma and skin rashes. Corticosteroids also lower immune system response. Many types of steroids exist. Learn about the different types, what they are used for, and safety considerations. Anabolic steroids are often used illegally to build muscle. But corticosteroids are used to treat a variety of health problems. Learn more about steroids. Steroid medicines (sometimes referred to as corticosteroids) are man-made (synthetic) versions of steroid hormones produced by the body. There are several different forms of steroid medicines. The form discussed in this leaflet is the tablet form, taken by mouth, called oral steroids. Hundreds of steroids are found in fungi, plants, and animals. All steroids are manufactured in cells from sterol precursors: cholesterol and lanosterol (in opisthokonts), or cycloartenol (in plants). All three of these molecules are produced via cyclization of the triterpene squalene. [4] Providers might refer to corticosteroids as glucocorticoids or the shortened term steroids. All of these names mean any synthetic medications that reduce inflammation in your body. Prednisone is a prescription corticosteroid (steroid) used to reduce inflammation, suppress an overactive immune system, and treat endocrine and metabolic disorders. Steroids are man-made medicines similar to natural body hormones, used to treat many conditions. They reduce inflammation and the activity of the immune system. Steroids come in various forms, including oral tablets, creams, nasal sprays, and inhalers. Side-effects are more common with oral steroids or long-term use. Find out more about steroids, the different types of steroid medicine, side effects and how to stop taking them safely.