Intercycle Serum Follicle-Stimulating Hormone Elevations: Significance in Recruitment and Selection of the Dominant Follicle and Assessment of Corpus Luteum Normalcy

Abstract

The significance of the intercycle elevation in serum FSH during recruitment and selection of the dominant follicle in the primate ovarian cycle was investigated. Five monkeys were laparotomized when serum estradiol levels exceeded 100 pg⁄ml, and the largest visable follicle was cauterized in two consecutive cycles, followed by uninterrupted ovarian function in the third cycle. Daily sera were collected for LH, FSH, estradiol, and progesterone determinations by RIA.Elevated serum estradiol concentrations were abruptly terminated after follicle cautery of the putative dominant follicle. The contiguous intervals from onset of menstrual flow to first ablation, then to the second ablation, and finally to the subsequent LH surge were 9.8 ± 1.4, 10.4 ± 1.6, and 13.7 ± 2.0 days, respectively. In addition, serum FSH levels were significantly lower (P < 0.03) than normal during the follicular phase of the cycle after follicle cautery. These data suggest that the timely recruitment, selection, and ovulation of the dominant follicle can continue without an antecedent FSH increase similar to that normally observed during the demise of the primate corpus luteum. Absence of the intercycle elevation in serum FSH in both women and monkeys displaying luteal phase defects suggests that this FSH pattern may enhance clinical assessment of corpus luteum normalcy.