Effect of gonadotrophin-releasing hormone (GnRH) antagonist during the LH surge in normal women and during controlled ovarian hyperstimulation

OBJECTIVE Several studies have suggested that GnRH is instrumental in trigg ering the LH surge. The present studies were performed to evaluate the effe ct of GnRH antagonist administration in women after the beginning of the LH surge. DESIGN In study one, six normal cycling women were given a GnRH antagonist (20 mg Nal Glu s.c.) during an unstimulated cycle. Nal-Glu was administered when the LH level was higher than 10 U/l and associated with an oestradiol (E2) level higher than 730 pmol/l. In study two, a GnRH antagonist (3 mg C etrorelix(R), ASTA-Medica, Frankfurt, Germany) was administered on day 8 of an IVF-ET cycle, in 157 women. Eighteen women among this cohort received t he antagonist, when their LH level was higher than 10 U/l. RESULTS In normal volunteers (study one), Nal-Glu was administered on day 1 3.7 +/- 1.4 (mean +/- SD) of the cycle when the LH level was 13.7 +/- 3.5 U /l with an E2 plasma level reaching 980 +/- 131 pmol/l. Twenty-four hours a fter administration of the antagonist, the LH surge had been interrupted in all subjects; it was postponed in three of the women, and abolished in the remaining three. LH levels fell by 68.5%, E2 by 42% and FSH by 53.2%. In s tudy two, LH plasma levels 24 h after the antagonist administration fell by 94%. No premature ovulation occurred in any of the patients treated. Admin istering the antagonist before (n = 139) or during the LH surge (n = 18) ma de no statistically significant difference to the results of the IVF-ET att empt. CONCLUSIONS Our results indicate that GnRH is required throughout the gonad otrophin surge in women, not only for the initiation but also for the maint enance of the LH surge. In addition, in our study, the suppression of the r ise in LH, when the antagonist was given during the surge, had no detriment al impact on IVF-ET outcome. This suggests, if confirmed on a larger scale, that late follicular phase GnRH antagonist administration to prevent the L H surge in controlled ovarian hyperstimulation (COH) is a safe and useful t reatment.