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Hormone Medication
The goal of hormonal treatment is to simulate pregnancy or menopause, two natural conditions know to inhibit the disease. With both treatments, the normal endometrium is no longer stimulated to grow and shed with each monthly cycle, and menstruation ceases. The growth of misplaced endometrial tissue will usually be suppressed as well.

Oral Contraceptives
To simulate the hormonal environment of pregnancy, your doctor may prescribe birth control pills to be taken in a pattern quite different from that used for contraception. One of the more effective regiments for endometriosis is to take the pills continuously, without pausing for withdrawal bleeding. If breakthrough bleeding occurs, the dose may be increased to two or three pills per day. Side effects associated with these higher dosages include nausea, water retention, and irregular vaginal bleeding. More serious complications, such as stroke, vascular problems, and heart disease, are rare but have been reported in susceptible woman.

As a contraceptive, birth control pills re administered one per day for three weeks each month, followed by a week without pills to permit menstrual flow. Many doctors feel birth control pills taken in this manner may prevent progression of endometriosis but although appealing, the theory has not been proven.

Danazol
The hormone derivative danazol is a medication frequently used to treat endometriosis. During treatment with danazol, estrogen levels are often reduced to low levels similar to natural menopause. This state is sometimes called pseudo-menopause. Danazol is thought to work indirectly by affecting the hormones produced by the brain which cause ovulation, and directly by affecting the endometrial implants.

Danazol is similar to male-specific hormones and may have side effects. These include, but are not limited to, deepening of the voice, abnormal hair growth, reduced breast size, water retention, weight gain, acne, irregular vaginal bleeding, and muscle cramps. Danazol controls pain in the majority of patients with less extensive endometriosis and may eliminate small patches of the disease. Unfortunately, large ovarian endometriomas (cysts) are generally resistant to the drug. Danazol is an expensive medication usually prescribed for six or more months and is associated with a high incidence of side effects.

GnRH Analogs
GnRH analogs comprise the newest class of hormones used for endometriosis treatment. After a few weeks of treatment, analog use leads to depletion of the pituitary hormones which direct the ovary to release estrogen. Estrogen levels fall to menopausal levels, ovulation does not occur, the endometrium does not grow, and menstruation does not occur. This results in a state called reversible menopause. Side effects of these drugs are associated with a lack of estrogen and include hot flashes, vaginal dryness, and loss of bone calcium. The medications are usually given for six months and can be administered as a daily or monthly injection or as a nasal spray. They are as effective as danazol in pain relief and in achieving pregnancy. Like danazol, large ovarian endometriomas (cysts) are generally resistant to GnRH analogs.

Progestins
Some doctors use progestins to treat endometriosis. Progestins are synthetic progesterone-like drugs prescribed as pill or injections. Side effects include water retention, mood swings, and irregular vaginal bleeding. They are considerably less expensive than the other medications. One special drawback of the injectable form is that it may inhibit fertility for an unpredictable period of time after treatment is discontinued.