Patterns of estradiol response in patients with endogenous gonadotropin surges during follicular recruitment in an in vitro fertilization and embryo transfer program.

This report is an analysis of 16 cycles in 15 patients stimulated with human menopausal gonadotropin and clomiphene citrate for the purpose of follicular recruitment in an in vitro fertilization program, all of which resulted in endogenous luteinizing hormone (LH) surges. A study of the pattern of estradiol (E2) response to stimulation revealed two groups of cycles, designated "leap" pattern (9 cycles) and "plateau" pattern (7 cycles), the rate of rise of E2 increasing or decreasing, respectively, as the time of the LH surge was approached. There were no significant differences between these groups of cycles in the peak E2 level attained or the number of follicles greater than or equal to 12 mm on the day of peak E2. In the plateau, but not in the leap pattern cycles, a significant correlation (r = 0.958) was found between the number of follicles greater than or equal to 12 mm and the peak E2. We tentatively conclude that "plateau" pattern cycles reflect relatively synchronous follicular recruitment; the greater the number of follicles recruited, the higher the E2 level attained, increased amounts of inhibin-like substances being available to restrain the LH surge; "leap" pattern cycles reflect asynchronous follicular recruitment.