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

In patients with anovulatory infertility the first choice of treatment for ovulationinduction is an antiestrogen, most commonly clomiphene citrate (CC). However, 20-25% of thewomen are resistant to CC and do not ovulate perhaps due to antiestrogenic mechanism of the CCaction, which involves long-lasting estrogen receptor (ER) depletion.

The objective of the study was to mimic the action of CC without depletion of ERs bythe 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.

20 patients with anovulation due to polycystic ovary syndrome (PCOS),who had previously inadequately responded to CC were selected for study. The aromatase inhibitorletrozole 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.

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 werecancelled due to absence of a dominant follicle (>1.4 cm).

Our study did not confirm the favorable effect of letrozole for induction ofovulation in patients with clomiphene resistant PCO.