Aromatase and endometriosis: estrogens play a role.

Endometriosis is an estrogen-dependent inflammatory disease defined by the growth of endometrial stroma and glands outside of the uterus. Epidemiological and clinical studies show that estrogen is essential for the growth of endometriosis. There are several molecular links between estrogen production and inflammation in endometriosis. The enzyme aromatase P450 is expressed aberrantly in endometriosis and is stimulated by prostaglandin E2 , resulting in production of estrogen that induces prostaglandin E2 expression within endometriotic lesions. Furthermore, estrogen promotes the secretion of several inflammatory cytokines and growth factors, which contribute to the progression of endometriosis and stimulate estrogen production. On the basis of the local estrogen biosynthesis in endometriotic implants, nonsteroidal aromatase inhibitors have been successfully used to treat pain symptoms caused by endometriosis. These agents do not cause the disappearance of endometriosis; they cannot be considered routine treatment and should only be administered in adequately controlled clinical studies.