Follicular and endocrine response to anastrozole versus clomiphene citrate administered in follicular phase to normoovulatory women: a randomized comparison

Objective: To compare the effect on follicular growth and endocrine parameters of follicular phase administration of anastrozole to healthy, normoovulatory women in doses of 1 or 5 mg, respectively, with the conventional dosing regimen for ovulation induction with clomiphene citrate (CC). Design: Randomized, assessor-blinded, single-center, three-armed study. Setting: University-affiliated, tertiary referral center. Patient(s): Thirty-two, normoovulatory, normogonadotropic women. Intervention(s): Administration of anastrozole 1 mg (group A1), anastrozole 5 mg (group A5), or CC 50 mg (group CC50) from cycle days 3 to 7. Main Outcome Measure(s): Number of follicles ≥15 mm and ≥10 mm on the day of the endogenous LH surge. Result(s): The mean number of follicles ≥15 mm on the day of LH surge was 1.4 ± 0.5, 1.0 ± 0.4, and 0.8 ± 0.4 in groups CC50, A1, and A5, respectively, which was statistically significant. Furthermore, a statistically significant difference between groups was found for the size of the growing follicular cohort (follicles ≥10 mm) on cycle days 8 and 10 and on the day of LH surge. The area under the curve (adjusted for baseline values on cycle day 3 and time frame of assessment) of follicular phase E₂ levels was significantly different among the groups that were compared (223.0 ± 97.5, 69.2 ± 40.0, and 83.4 ± 36.4 for groups CC50, A1, and A5, respectively). Conclusion(s): CC 50 mg exerts a stronger stimulatory effect on follicular growth compared with anastrozole in doses of 1 or 5 mg. Anastrozole administration results in lower follicular phase E₂ levels.