Steroid, << STEHR oyd, >> is any of a class of chemical compounds important in chemistry, biology, and medicine. Steroids play a key role in the body processes of living things. They are produced naturally by plants and animals. They are also made commercially. Steroids include sterols, such as cholesterol; bile acids from the liver; adrenal hormones; sex hormones; and poisons in certain toads (see Cholesterol ; Liver ).
All steroids are alike in basic chemical structure. But each steroid has a slightly different arrangement of atoms. Because of this difference, steroids have different effects on living things. Also, individual organisms may react differently to the same steroid.
Steroids influence body metabolism, the process by which the body changes food into energy and living tissue. In plants, they help form certain vitamins and other important substances. Some steroids are used in medicine to treat diseases. Digitalis, a plant steroid, is often used to treat heart failure (see Digitalis ).
The sex steroids
progesterone and estrogens are primarily secreted by the ovaries (female sex organs). Progesterone helps regulate menstruation and maintain pregnancy. Estrogens are essential for female sexual development, including the development of breasts. Birth control pills contain powerful synthetic forms of progesterone. Some birth control pills also contain estrogens (see Birth control ).
Androgens are sex steroids that are chiefly produced by the testes (male sex glands). Androgens are responsible for maturation of the male’s sex organs and his beard, large muscles, and deep voice. Small amounts of androgens are also secreted by the sex glands in females. Similarly, male sex glands produce small amounts of estrogens.
Anabolic steroids are produced by chemical methods from the male hormone testosterone. Some athletes use anabolic steroids because the drugs increase strength and body weight. However, this use of anabolic steroids is considered unethical. In addition, the use of these drugs can cause many undesirable effects. These include liver damage, high blood pressure, aggressive behavior, and the appearance of male physical characteristics in females. The use of anabolic steroids in most sports competition is prohibited.
The adrenal steroids.
The cortex (outer layer) of the adrenal gland produces cortisol, corticosterone, and small amounts of cortisone. These steroids help regulate protein and carbohydrate metabolism. Aldosterone, another steroid from the adrenal cortex, influences mineral and water balance of the body.
Doctors use adrenal steroids to reduce inflammation (redness and swelling) and to provide treatment for arthritis, allergies, and other diseases. If the adrenal glands are surgically removed, a person will die unless treated with steroids.
The steroid secretion of the ovaries, testes, and adrenal glands is regulated by a part of the brain called the hypothalamus. The hypothalamus controls the release of the protein hormones gonadotropins and adrenocorticotropic hormone (ACTH) from the pituitary gland. The hormones cause the ovaries, testes, and adrenal glands to release their steroids. The steroids then affect other body parts and characteristics.
