Steroids
Steroids are any one of a large number of compounds that are related to sterols. Steroids include bile acids, D vitamins, certain hormones, and certain carcinogenic substances. Sterols are alcohols with a cyclic nucleus. An example of a steroid is cholesterol. In the human organism, cholesterol is the parent compound of all steroid hormones.
The accompanying illustration shows some of the most important steroid hormones. Their similarity to cholesterol is obvious. In the adrenal glands located above the kidneys, the synthesis of hydrocortisone, aldosterone, and a portion of the body's testosterone are produced. All human females produce a small amount of testosterone in this manner. It is the testes of males, however, that synthesize the greatest quantity of testosterone and account for male secondary sexual characteristics (e.g. facial hair, deep voice, etc.) In the ovaries of the female, estrogens and other female hormones are produced. Estradiol is an example of an estrogen, and it is also the basis for most oral contraceptives. Also illustrated are some synthetic steroids. Ethynyl estradiol combined with norethindrone form the mixture of the majority of birth control pills. These molecules fit receptor sites for naturally produced hormones and trick the body into a false state of pregnancy, so no egg is ever released from the ovaries. Conversely, RU-486d, binds strongly to progesterone receptors and prevents a fertilized egg from implanting in the uterus. This has been commonly known as the "morning after" pill.
Important in all these steroidal compounds is their stereochemistry or 3- dimensional configuration. These molecules are not flat, but rather, they take on a shape that complements their receptor site. Thus, their synthetic counterparts must also have the proper stereochemistry.
The glucocorticoids and mineralocorticoids synthesized in the adrenal gland are vital for homeostasis and response to stress and physical trauma. Androgens such as testosterone are builders of muscle mass in males and females. A number of synthetic compounds based on testosterone have been developed in the hope of keeping a severely debilitated patient (such as a major burn victim) from catabolizing their own muscle tissue. Nandrolone is such a compound; unfortunately, athletes began to abuse such androgens by taking massive doses in an effort to build greater body muscle mass and strength. This strategy remains unproven, however, and the side effects of virilization in females, breast development in males, liver toxicity, inappropriately aggressive behavior, and even death forced the United States Food and Drug Administration to make such compounds a scheduled substance along with narcotics. Some athletes have gone to veterinary drugs in an effort to circumvent such regulation.
Adrenal steroids are absolutely essential for body homeostasis. The glucose control and significant anti-inflammatory actions of hydrocortisone are so vital that death ensues within 72 hours if the body is deprived of this substance. Used in higher than normal doses to treat inflammatory diseases such as lupus, rheumatoid arthritis, and asthma, the complications are myriad and include gastrointestinal ulceration, chemical diabetes, and over suppression of the immune response resulting in uncontrolled infection, sepsis,, multiple organ failure, and death. Aldosterone is also an essential adrenal hormone that causes the kidneys to retain sodium and water, exactly what is required in states of dehydration or blood loss. However, in a patient with high blood pressure (hypertension) having the ability to block aldosterone is often advantageous. Spirinolactone was synthesized to act in just such a manner and is extremely successful.
Obviously, the chemistry and biochemistry of steroids is extremely complex, but as chemists unravel the mysteries of molecules and their receptor site activities, this huge but magnificent puzzle begins to be solved.
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