Northwestern University Feinberg School of Medicine

Department of Obstetrics and Gynecology

Treatment of Endometriosis with Aromatase Inhibitors

Treatment with aromatase inhibitors is the most commonly used form of nontoxic treatment in postmenopausal breast cancer. Aromatase is the key enzyme for estrogen formation in human tissues. Our reseach recently showed large amounts of aromatase thus estrogen formation in endometriosis. Inhibition of this enzyme in animal models and human disease decreased inflammation and growth in endometriosis and significantly reduced pain associated with endometriosis. In postmenopausal women, use of an aromatase inhibitor in combination with a bisphosphonate is the treatment of choice in patients who do not respond to surgical resection.

In premenopausal women, aromatase inhibitors are used in combination with an additional drug that suppresses the ovaries because aromatase inhibitor-only treatments may give rise to ovarian stimulation. This additional drug may be a GnRH agonist (eg, Zoladex), progestin (eg, norethindrone acetate) or a birth control pill (eg, Alesse). Currently, some physicians prescribe these regimens to treat premenopausal endometriosis not responding to currently available treatments or in patients who cannot use existing treatments because of their side effects. The majority of these premenopausal patients respond favorably having decreased pelvic disease and reduced pain. Treatment of endometriosis with aromatase inhibitors is still considered experimental, since there are no current efforts known to the public for obtaining FDA approval for their use in treating endometriosis.

The side effects of aromatase inhibitors include mild hot flashes and decreased libido. If aromatase inhibitors are administered alone to postmenopausal women, they cause osteoporosis and should be combined with a bisphosphonate. In premenopausal women, the combination of an aromatase inhibitor with a progestin or birth control pill does not cause osteoporosis, whereas that combination with a GnRH agonist (eg, Zoladex) causes osteoporosis.

Suggested Reading

Clinical Trials and Case Reports (Aromatase Inhibitors for Treatment of Endometriosis)

Reviews and Original Articles on the Role of Aromatase in Endometriosis

Articles on the Use of Aromatase Inhibitors in Breast Cancer

Articles on the Use of Aromatase Inhibitors for Ovulation Induction

Contact Information

Serdar E. Bulun, MD
John J. Sciarra Professor
Chair, Department of Obstetrics and Gynecology
Feinberg School of Medicine at Northwestern University
303 E. Superior St.
Ste. 4-123
Chicago, IL 60611