Pauline Condon, age 14, of Johnson City, Tenn., for her question:

WHAT DOES A STEROID DO?

A steroid is a class of chemical compounds that are important in chemistry, biology and medicine. They play an important part in the body processes of living things.

Steroids 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; and sex hormones.

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.

Estrogen and progesterone are two sex steroids given off by the ovaries, which are female sex organs. These steroids are responsible for the female’s smooth, soft skin; rounded hips; high pitched voice; and the development of the breasts.

Androgens are sex steroids that are produced by the testes, which are male sex glands. Androgens are responsible for the male’s beard, large muscles and deep voice. They may even influence personality traits such as aggressiveness, which is considered a male characteristic.

The adrenal steroids are present in both sexes. The cortex or outer layer of the adrenal gland produces cortisole, corticosterone and small amounts of cortisone. These steroids help regulate protein and carbohydrate metabolism.

Other steroids from the adrenal cortex influence mineral and water balance of the body.

All steroids are alike in basic chemical structure. But each steroid has a slightly different arrangement of molecules. Because of this difference, steroids have different effects on living things. Also, individual organisms may react differently to the same steroid.

Doctors use adrenal steroids to reduce inflammation, which is redness and swelling from injury. They also use it to treat arthritis, skin diseases, allergies and many other diseases.

If the adrenal glands are surgically removed, a person will die unless he receives treatments with steroids.

Scientists first obtained cortisone for commercial use from adrenal glands. Today, most of it is produced in laboratories by chemical methods. Other kinds of steroids are also made for commercial uses in medicine.

The normal steroid secretion of the ovaries, testes and adrenal glands is regulated by a small part of the brain called the hypothalamus. The hypothalamus controls the release of the powerful protein hormones gonadotropin and adrenocorticotropic hormone (ACTH) from the pituitary gland.

These hormones cause the ovaries, testes and adrenal glands to release their steroids. The steroids then affect other body parts and characteristics.