Steroids vs Hormones
Steroids, like soaps, fatty acids, sphingolipids, and prostaglandins, are examples of Lipids that do not have the ester functional groups (non glyceride Lipids). Lipids are bio-molecules that are soluble in organic non-polar solvents. As such, fats and lipids are insoluble in water. Lipids and fats are important to the body because they serve as sources of energy, and also store energy in form of fat cells. Lipids are structural components in cell membranes, and this is their major cellular function. Hormone steroids and prostaglandins act as chemical messengers between body tissues.
Steroids form one of the major classes of lipids, and have a structure that is greatly different from that of other classes of lipids. Their structure features a unique, 3-ringed system of cyclohexanes, fused with one ring of cyclopentane. Various functional groups may be attached to the ring. Like in all lipids, the main feature in the structure, which makes steroids non-polar, is the large number of carbon-hydrogens. Well known examples of steroids include sex hormones, cholesterol, cortisone, birth control pills, and anabolic steroids. Cholesterol is the most well known, and the most abundant steroid in the body. It is made in brain tissue, nerve tissue and in the blood stream. It forms the major component of gall stones and bile salts, as well as contributing to the formation of deposits on the inner walls of blood vessels.
Another well known example of steroids, is the sex hormones: Testosterone for males, and progesterone and estrogen for females. In males, testosterone is primarily responsible for the development of secondary sexual traits, while the female hormones control the process of ovulation. Worth noting, is the fact that male and female hormones differ slightly in structure, yet their physiological effects are starkly different.
Sexual traits in males that are promoted by testosterone include a deep voice and bodily hair. Normal growth of the male genitalia is also promoted by testosterone. In females, estrogen, together with progesterone, regulates the variances that occur in the uterus and ovaries, and is responsible for the menstrual cycle.
There are also hormones known as adrenocorticoid hormones, which are produced by the adrenal glands. Aldosterone is the most important of the mineralocrticoids. Its function is to regulate the re-absorption of sodium and chloride ions in the kidney, while increasing the loss of potassium ions. Swelling in tissues is also controlled by aldosterone. The most important glucocortinoid is Cortisol, whose function is to increase the concentration of glucose and glycogen in the body.
Summary:
Most hormones are mainly used in body processes, and therefore, are useful in the body, while not all steroids are useful in the body.