Comparison of endocrine and ultrasound profiles during ovulation induction with clomiphene citrate and letrozole in ovulatory volunteer women.

OBJECTIVE

To compare endocrine and follicular dynamics in ovulatory volunteer women in natural cycles and cycles stimulated with clomiphene (CC) and letrozole (LE).

DESIGN

Prospective, randomized, double-blind, crossover study.

SETTING

A private tertiary fertility center.

PATIENT(S): Thirty ovulatory volunteer women (<39 years).

INTERVENTION(S): Randomized ovarian stimulation with CC and LE compared with no treatment.

MAIN OUTCOME MEASURE(S): Hormone profiles, follicular development, and endometrial development through the cycles.

RESULT(S): The LE-treated cycles had the shortest follicular phase (13.1 vs. 13.9 days with CC) with less multiple follicular development than CC. They showed higher midfollicular LH concentrations (7.5 IU/L vs. 6.0 IU/L), lower LH surge values (27.9 IU/L vs. 44.4 IU/L), and lower E(2) concentrations than natural cycles. The LE cycles showed significant increases in free androgen index in the midfollicular phase compared with the CC cycles. Endometrial thickness in LE cycles (8.3 mm) was similar to natural cycles, whereas in CC cycles it was reduced (7.6 mm vs. 8.5 mm) compared with natural cycles. Ovulation profiles were similar in all cycles.

CONCLUSION(S): The LE treatment of normal women led to multiple follicular development, but less than CC. Estradiol concentrations were reduced, follicular phase length was shorter, whereas endometrial thickness and luteal P were normal. Follicular phase increased free androgen index is a novel finding and may explain the physiological observations.