Key Points

• Aromatase inhibitors (AIs) are pharmacologic agents that block the conversion of androgens to estrogens
• There is some evidence that AIs may reduce leiomyoma volume to a degree that is similar to GnRH agonists
• Aromatase inhibitors are a therapeutic option for the management of uterine leiomyomas.
• AIs have been shown to decrease menstrual volume, the duration of menstruation, and the presence or severity of dysmenorrhea.
• Associated adverse effects of IAs include hot flushes, vaginal dryness, and musculoskeletal pain
• At this time, there are limited studies and consequently no regulatory approval of these agents for use in the treatment of leiomyoma related symptoms

Aromatase inhibitors represent a class of antiestrogens widely used in gynecology for a number of indications including the induction of ovulation. The physiological action  of aromatase is the  synthesizes of estrogens from androgens; consequently aromatase inhibitors block the synthesis of estrogens. The available aromatase inhibitors include  letrozole, anastrozole, and fadrozole. AI use has been shown to reduce fibroid volume by 46% after 12 weeks of treatment (1).

One study evaluated the use of letrozole 5 mg/day orally for 3 months, it was evidenced that the use of this drug significantly reduced the size of uterine leiomyomas (P < 0.01) and benefited women with heavy menstrual bleeding associated with leiomyomas without changing bone mineral density (2). 

Regarding preoperative management with letrozole, its use before laparoscopic myomectomy was associated with a significant decrease in total operative time, time required to perform hysterorrhaphy and less intraoperative bleeding (3).

Islam MS, Protic, O, Giannubilo SR, Toti P, Tranquilli AL, Petraglia F, et al. Uterine leiomyoma: available medical treatments and new possible therapeutic Options. J Clinic Endocrionol Metabolism 2013;98:821-34

1. Song H, Lu D, Navaratnam K, Shi G. Aromatase inhibitors for uterinebfibroids. Cochrane database Syst Rev. 2013 Oct;(10):CD009505.

2. Gurates B, Parmaksiz C, Kilic G, Celik H, Kumru S, Simsek M. Treatment ofbsymptomatic uterine leiomyoma with letrozole. Reprod Biomed Online. 2008bOct;17(4):569–74.

3. Leone Roberti Maggiore U, Scala C, Venturini PL, Ferrero S. Preoperativebtreatment with letrozole in patients undergoing laparoscopicbmyomectomy ofblarge uterine myomas: a prospective non-randomized study. Eur J ObstetbGynecol Reprod Biol. 2014 Oct;181:157–62.