Aromatase Inhibitors for Ovulation Induction

Abstract

Preliminary evidence suggests that AIs may replace CC in the future because of similar efficacy with a reduced side effect profile. Although worldwide experience with AIs for ovulation induction is increasing, at present, definitive studies in the form of randomized controlled trials comparing CC with AIs are lacking.

Letrozole versus Clomiphene for Infertility in the Polycystic Ovary Syndrome

“…This hormonal profile, against expectations, 6 probably led to a thinner endometrium during the midluteal phase. Our previous study 18 showed that a higher baseline level of sex hormone-binding globulin, as compared with a lower level, and a lower free androgen index at baseline, as compared with a higher index, were associated with an increased live-birth rate.…”

“…5 Aromatase inhibitors, which block estrogen synthesis, directly affect hypothalamic-pituitary-ovarian function and theoretically might increase pregnancy rates. 6 Potential advantages of aromatase inhibitors over selective estrogen-receptor modulators include a more physiologic hormonal stimulation of the endometrium, a lower multiple-pregnancy rate through singlefollicle recruitment, a better side-effect profile with fewer vasomotor and mood symptoms, and more rapid clearance, thus reducing the chances of periconceptional exposure. 6 However, potential fetal teratogenicity remains a concern with letrozole (see the Supplementary Appendix, available with the full text of this article at NEJM.org).…”

“…6 Potential advantages of aromatase inhibitors over selective estrogen-receptor modulators include a more physiologic hormonal stimulation of the endometrium, a lower multiple-pregnancy rate through singlefollicle recruitment, a better side-effect profile with fewer vasomotor and mood symptoms, and more rapid clearance, thus reducing the chances of periconceptional exposure. 6 However, potential fetal teratogenicity remains a concern with letrozole (see the Supplementary Appendix, available with the full text of this article at NEJM.org). 7 We designed a double-blind, multicenter, randomized trial to test the hypothesis that letrozole would be superior to clomiphene as an infertility treatment and would have a similar safety profile.…”

Randomized controlled trial of Letrozole versus Clomiphene citrate for induction of ovulation in polycystic ovarian syndrome (PCOS): A Malaysian experience

“…A single dominant follicle and monoovulation should occur in most cases [8]. In the endometrium, estrogen receptors may be upregulated, resulting in rapid endometrial growth once estrogen secretion is restored following clearance of Letrozole [9].…”

Fertility management in the PCOS population: results of a web-based survey at IVF-worldwide.com

“…The use of aromatase inhibitors (AI) was only 8 %. This is interesting as AIs have been promoted by some as especially advantageous in ovulation induction of the PCOS patient [2,7,10]. Even though AIs appear to be safe in terms of fetal teratogenic risks [15], Novartis, the producer of Letrozole, states that it is only indicated for postmenopausal women and it is contraindicated in women who may become pregnant (http:// www.pharma.us.novartis.com/product/pi/pdf/Femara.pdf).…”