Antiandrogens, also known as androgen antagonists or testosterone blockers, are a group of hormone receptor antagonist compounds that can prevent or inhibit the biological effects of androgens, male sex hormones, on sensitive tissues in the body. Antiandrogens usually work by blocking receptors. These compounds work by blocking the biological effects of androgens, or male sex hormones, through blocking or competing for cellular binding sites. By inhibiting testosterone’s ability to bind, these androgen antagonists cause a reduction in overall testosterone production in the body.
Doctors prescribe antiandrogens to treat a variety of problems, including prostate cancer, acne, and male pattern baldness. They have shown success in treating polycystic ovary syndrome (PCOS) and are commonly used to relieve symptoms of hirsutism or excessive hair growth. They are used by transgender women during sex reassignment therapy and to treat male sexual disorders. Some registered sex offender programs administer antiandrogens to offenders to reduce sexual desire and the risk of recidivism.
During the treatment of prostate cancer, antiandrogens reduce testosterone production. Hormone receptor antagonists are often given before and after radiation therapy. In combination with other hormone therapies, antiandrogens slow the progression of prostate cancer and can relieve pain if the cancer has spread to nearby bones. Research has shown that the use of androgen antagonists increases the survival rate for men diagnosed with prostate cancer.
There are two types of these antiandrogens: pure or non-steroidal and steroidal. Flutamide is an example of a pure antiandrogen. It is one of the primary drugs prescribed during the treatment of prostate cancer 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 symptoms of acne or hair loss. When given to males, this medication should not be accompanied by potassium supplementation to reduce the risk of hyperkalemia or abnormally high levels of potassium in the blood.
Ketoconazole, another commonly prescribed antiandrogen, functions as a broad-spectrum antifungal. Drugs such as finasteride and dudasteride treat male pattern baldness. Other synthetic steroid antiandrogens are included in birth control pills.
Side effects caused by treatment with antiandrogens include nausea, diarrhea, reduced sex drive, difficulty getting an erection, low red blood cell count, enlarged breasts and liver problems. Long-term use can lead to osteoporosis, a disease that causes bones to become brittle and break.
Antiandrogens are absolutely contraindicated during pregnancy. Research clearly shows that male fetuses exposed to androgen antagonists in utero undergo permanent demasculinization. Side effects noted by male rate studies include genital malformations such as hypospadias and cleft phallus, absent or reduced sex accessory glands, and nipple retention.