monally induced changes in the ectopic tissue. Common medical therapies include danazol and gonadotropin-releasing hormone (GnRH) agonists, neither of which is uniformly successful. Surgical therapy is sometimes uses as well, particularly when endometriosis is associated with infertility. The side effects of the currently available therapies for treating endometriosis are sufficient to warrant continued research on alternative treatments. Further, drug and surgical treatments are only palliative, and it would be an important advance to have a curative treatment.

Human studies using antiprogestins to treat endometriosis are limited. Only a single antiprogestin (mifepristone) has been evaluated, and treatment periods have been short (three and six months). In these limited studies, mifepristone at several different doses produced uniform amenorrhea and reduced pain in all subjects. However, significant disease regression was observed only with longer treatment (six months). Daily administration of mifepristone in this context seemed to be well tolerated, with limited side effects, particularly at the lowest doses studied (<25 mg/day). A study using 5 mg/day of mifepristone for six months is ongoing and will establish whether dosages this low are effective in treating endometriosis.

The main promise offered by antiprogestins for treating endometriosis is preservation of the follicular phase levels of estradiol. This would protect women from the consequences of very low estrogen levels encountered with other forms of therapy (e.g., GnRH agonist). A goal of therapeutic studies should be to develop an antiprogestin regimen that is devoid of antiglucocorticoid side effects such as fatigue, nausea, and vomiting.

Uterine Leiomyomas (Fibroids)

Uterine leiomyomas, also known as fibroids, are non-malignant tumors of smooth muscle cell origin. Leiomyomas are the most common pelvic tumor; some have estimated that up to 20 percent of women over 30 years of age may have these benign tumors. They represent one of the most frequent reasons for surgery (including hysterectomies) in women of reproductive age.

These tumors are clearly hormonally dependent. Medical therapies such as high-dose progestin therapy and gonadotropin-releasing hormone agonists decrease overall uterine volume markedly, usually over a three-month treatment period. However, the effect of medical therapy is temporary, and no therapy has thus far been successful on a long-term basis. In the face of persistent symptoms, surgical therapy is usually applied in advanced disease following the failure of medical therapy and, ideally, when no pregnancies are desired.

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