Hormonal profile and endometrial morphology in letrozole-controlled ovarian hyperstimulation in ovulatory infertile patients.

OBJECTIVE To evaluate the clinical response and endometrial morphology during the implantation window on ovarian hyperstimulation with the aromatase inhibitor letrozole in infertile ovulatory women. DESIGN Prospective trial in infertile patients. SETTING Tertiary care hospital. PATIENT(S) Eight ovulatory infertile patient candidates for ovarian superovulation. INTERVENTION(S) Subjects were monitored in one control cycle. In the next cycle, they received letrozole 5.0 mg daily on days 3 through 7 after menses. MAIN OUTCOME MEASURE(S) Number of ovulatory follicles; dominant follicle diameter; endometrial thickness; hormonal profile of FSH, LH, E(2), A, T, and P; endometrial histological dating; and pinopode formation assessed by scanning electron microscopy. RESULT(S) Cycles stimulated with letrozole resulted in more ovulatory follicles than did natural cycles (mean +/- SD 2.0 +/- 0.9 vs. 1.0 +/- 0.0), which attained a greater preovulatory diameter (mean +/- SD 23.8 +/- 2.7 vs. 19.3 +/- 2.1 mm), with similar endometrial thickness at midcycle compared with spontaneous cycles. Endocrine profile of medicated cycles was characterized on day 7 by increased levels of LH (5.9 +/- 0.8 vs. 3.5 +/- 0.4 IU/mL), reduced E(2) (98.4 +/- 11.4 vs. 161.5 +/- 14.7 pmol/L), and elevated androgens. Preovulatory and midsecretory E(2) were similar to spontaneous cycle, and P levels during midluteal phase were significantly elevated (44.2 +/- 4.6 vs. 27.7 +/- 4.6 pmol/L). Endometrial morphology during the implantation window in letrozole-stimulated cycles was characterized by in-phase histological dating and pinopode expression on scanning electron microscopy. CONCLUSION(S) Letrozole induces moderate ovarian hyperstimulation in ovulatory infertile patients with E(2) levels similar to spontaneous cycles and higher midluteal P, leading to both a normal endometrial histology and development of pinopodes, considered to be relevant markers of endometrial receptivity.