steroids, class of lipids having a particular molecular ring structure called the cyclopentanoperhydro-phenanthrene ring system. Steroids differ from one another in the structure of various side chains and additional rings. Steroids are common in both plants and animals. In humans, steroids are secreted by the ovaries and testes, the adrenal cortex (see adrenal gland), and the placenta.
The range of steroids is diverse, including several forms of vitamin D, digitalis, sterols (e.g., cholesterol), and the bile acids. Many steroids are biologically active hormones that control a number of the body's metabolic processes. This group includes the male sex hormone testosterone and the female sex hormones estrogen and progesterone. The steroid hormones of the adrenal cortex include glucocorticoids such as cortisone and cortisol (see also corticosteroid drug) and mineralocorticoids such as aldosterone.
Natural or synthetic steroids are used in oral contraceptives and in the treatment of arthritis, Addison's disease, and certain skin ailments. Side effects, related to dosage and length of treatment, can be serious and include high blood pressure, edema, unwanted hair growth, and menstrual cycle disruption. Anabolic steroids, male hormones given to build up strength in seriously ill patients, have been abused by bodybuilders and athletes in an attempt to increase muscle mass and strength.