Luteal phase oestradiol suppression by letrozole: a pilot study in oocyte donors.

This prospective randomized controlled pilot study was conducted in a tertiary referral university hospital to evaluate whether the administration of letrozole in the luteal phase of stimulated IVF cycles, through a decrease in oestradiol, could alter the suppressed LH levels in the luteal phase. Following oocyte retrieval, six oocyte donors aged < or = 36 years were randomized to receive either 5 mg letrozole (n = 3) or placebo (n = 3). On days 4, 7 and 10 after human chorionic gonadotrophin (HCG) administration, oestradiol levels of the letrozole group were significantly lower compared with the placebo group (P = 0.008, P =0.005 and P =0.004, respectively). LH and progesterone values were comparable between both groups at all time points measured. This study demonstrates that the addition of 5 mg of letrozole in the luteal phase of stimulated donor IVF cycles significantly alters the oestradiol levels on days 4, 7 and 10 after HCG administration for final oocyte maturation. The progesterone and LH profiles of patients treated with letrozole during the same period were not altered compared with the placebo group.