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Antiandrogens are hormone receptor antagonists. These compounds work by blocking the biological effects of androgens, or male sex hormones, through the obstruction of or competition for cell binding sites. By inhibiting the ability for testosterone to bind, these androgen antagonists cause a reduction in overall testosterone production in the body.
Physicians prescribe antiandrogens to treat a variety of issues, including prostate cancer, acne and male pattern baldness. They have shown success in the treatment of polycystic ovarian syndrome (PCOS) and are commonly used to relieve the symptoms of hirsutism, or excessive hair growth. They are used by transsexual women during sex reassignment therapy and to treat male sexual disorders. Some registered sex offender programs administer antiandrogens to offenders to reduce sexual drive and the risk of repeat offenses.
During the treatment of prostate cancer, antiandrogens lower testosterone production. Hormone receptor antagonists are often administered before and after radiation therapy. When combined with other hormone therapies, antiandrogens slow the progression of prostate cancer and can ease pain if the cancer has spread to nearby bones. Research has shown that the use of androgen antagonists increases the rate of survival for men who have been diagnosed with prostate cancer.
There are two types of these antiandrogens: pure, or nonsteroidal, and steroidal. Flutamide is an example of a pure antiandrogen. It is one of the primary drugs prescribed during prostate cancer treatment and lowers excess androgen levels in women with PCOS.
Spironolactone is classified as a steroidal androgen antagonist. This diuretic is commonly prescribed in the treatment of hirsutism. Women suffering from PCOS often experience a successful reduction in their symptoms of acne or hair loss. When given to males, this drug must not be accompanied by potassium supplementation to decrease the risk of hyperkalemia, or abnormally high levels of potassium in the blood.
Ketoconazole, another commonly prescribed antiandrogen, works as a broad-spectrum anti-fungal. Drugs such as finasteride and dudasteride treat male pattern baldness. Other synthetic steroid antiandrogens are included in birth control pills.
Side effects caused by antiandrogen treatment include nausea, diarrhea, decreased sex drive, erection difficulties, low red blood cell count, breast enlargement and liver problems. Long-term use can lead to osteoporosis, a disease that causes bones to become brittle and break easily.
Antiandrogens are absolutely contraindicated during pregnancy. Research clearly shows that male fetuses exposed to androgen antagonists in utero suffer permanent demasculinization. Side effects noted from the studies of male rates include genital malformations such a hypospadias and cleft phallus, absent or reduced sex accessory glands and the retention of nipples.