Long‐term mifepristone (RU486) therapy resulting in massive benign endometrial hyperplasia

Mifepristone (RU486) is a potent antiprogestagen, and at high doses it also acts as an antiglucocorticoid drug. Mifepristone, administered as a single 600 mg dose, is commonly employed to induce medical abortion in conjunction with prostaglandins. The long‐term safety profile of mifepristone, especially at high doses, is less well‐established. Long‐term mifepristone is considered efficacious in treating uterine myomas, endometriosis (25–100 mg/day), and possibly in inoperable meningiomas (200 mg/day), as well as inoperable Cushing's syndrome. Many animal studies document an antiproliferative effect (antioestrogenic), as do some reports in humans. However, there are also data to suggest that, as an antiprogestagen, mifepristone may promote an unopposed oestrogen milieu, and thus have a proliferative effect upon the endometrium.