GnRH-agonist triggering for final oocyte maturation in GnRH-antagonist IVF cycles induces decreased LH pulse rate and amplitude in early luteal phase: a possible luteolysis mechanism

The use of GnRH agonist to trigger final oocyte maturation in GnRH-antagonist in vitro fertilization (IVF) cycles has been shown to significantly reduce or even eliminate the risk of ovarian hyperstimulation syndrome (OHSS) by inducing rapid luteolysis early in the luteal phase. The exact mechanism of this early luteolysis is still widely unknown. Since luteinizing hormone (LH) has a major role in corpus luteum support, we sought to explore the pattern of LH secretion early in the luteal phase. Ten high risk patients for developing OHSS and triggered with GnRH agonist were included. Frequent blood sampling (every 20 min for 6 h) to measure LH, estradiol and progesterone was done on the day of oocyte collection (n = 5, Group 1) and on the day of embryo transfer, 48 h after oocyte collection (n = 5, Group 2). We found that the mean LH concentration and its secretion rate decreased significantly in Group 2 compared to Group 1. Both groups had similar number of LH pulses characterized by very small amplitude. In Group 2, there was a steady significant decrease in estradiol and progesterone over time. The results of this study show that LH secretion deviates significantly from normal physiologic pattern, which can explain, at least in part, the post-GnRH-agonist trigger early luteolysis mechanism.