GnRH antagonists do not activate the GnRH receptor

Recent suggestions that gonadotrophin-releasing hormone (GnRH) antagonists activate the GnRH receptor are discussed. Most of the studies cited in supp ort of this suggestion are in-vitro studies, testing supra-pharmacological doses of GnRH analogues in cancer cell lines, whereas GnRH antagonists, e.g . ganirelix or cetrorelix, do not affect the steroidogenesis of human granu losa cells in vitro, In patients treated with GnRH antagonists prior to IVF or intracytoplasmic sperm injection (ICSI), oocyte maturity and fertilizat ion rates are equal to those achieved following a long protocol of GnRN ago nists. Although there is a tendency towards a lower pregnancy rate (not sta tistically significant) in the initial trials using GnRH antagonist with ei ther recombinant FSH or human menopausal gonadotrophin (HMG) for ovarian st imulation, this ne rv treatment option of GnRH antagonists facilitates shor t and simple treatment and improves the convenience and safety for the pati ent. As with GnRH agonists in the past, the clinical outcome of GnRH antago nist treatment will improve with time as more clinical experience is gained (learning curve) and the treatment protocol is optimized. Moreover, a GnRH agonist instead of human chorionic gonadotrophin (HCG) may be used for tri ggering ovulation and will decrease the cancellation rate and minimize the risk for developing ovarian hyperstimulation syndrome (OHSS).