Comparison of the effectiveness of recombinant and urinary FSH preparations in the achievement of follicular selection in chronic anovulation.

In order to compare the effectiveness of urinary and recombinant FSH (rFSH) preparations in achieving the threshold of follicular growth, stimulated cycles from patients with chronic anovulation, treated with a constant dose of FSH until the emergence of a selected follicle, were retrospectively analysed. Sixty-four cycles were performed using a similar starting dose of either urinary FSH (group 1) or rFSH (group 2), which was kept constant up to the time of follicular selection, assessed on ultrasound (follicular diameter >10 mm). The results of this study showed that, while the number of selected follicles was similar, the mean daily FSH dose required to achieve the threshold of follicular selection was significantly lower in group 2 (70.4 +/- 3.4 IU/day) than in group 1 (86.5 +/- 4 IU/day; P < 0.005). Furthermore, at the time of human chorionic gonadotrophin (HCG) administration, the total FSH dose was significantly lower in group 2 than in group 1, but plasma oestradiol values were equivalent. These data suggest that the higher effectiveness of rFSH preparations over urinary ones may be explained by a lower threshold dose required to achieve follicular selection.