The Effect of Letrozole in Induction of Ovulation in Clomiphene Resistant Patients

Background: In patients with anovulatory infertility the first choice of treatment for ovulation induction is an antiestrogen, most commonly clomiphene citrate (CC). However, 20-25% of the women are resistant to CC and do not ovulate perhaps due to antiestrogenic mechanism of the CC action, which involves long-lasting estrogen receptor (ER) depletion. Objective: The objective of the study was to mimic the action of CC without depletion of ERs by the administration of an aromatase inhibitor letrozole in a selected group of Poly Cystic Ovary (PCO) patients who demonstrated failure to ovulate after treatment with CC. Materials and Methods: 20 patients with anovulation due to polycystic ovary syndrome (PCOS), who had previously inadequately responded to CC were selected for study. The aromatase inhibitor letrozole was administered orally in a dose of 2.5 mg on days 3-7 of the menstrual cycle. Then, occurrence of ovulation, endometrial thickness, and pregnancy rates were determined. Result(s): Only one patient had one dominant follicle (1.8 cm diameter) on day 14 of the cycle (estradiol = 200 pg/ml). IUI was done; however, no pregnancy took place. In the remaining cases, several sonographies were done between days 9 to 15 of the cycle; however, all cycles were cancelled due to absence of a dominant follicle ( > 1.4 cm). Conclusion(s): Our study did not confirm the favorable effect of letrozole for induction of ovulation in patients with clomiphene resistant PCO.