Extrapituitary effects of GnRH antagonists in assisted reproduction: a review

GnRH antagonists are used to prevent premature LH surges in assisted reproduction. The pregnancy rates obtained in several studies have been similar to those obtained in the long protocol with gonadotrophin-releasing hormone (GnRH) agonists. However, lower oestrogen serum concentrations have been observed and fewer oocytes retrieved using GnRH antagonists. Thus, potential effects at extrapituitary GnRH receptors in the ovary and the endometrium have been claimed. The article reviews the currently available data from the literature as well as current investigations with respect to effects of cetrorelix on the ovary and the endometrium. No evidence was found to support the hypothesis of extrapituitary effects of GnRH antagonists such as cetrorelix at doses used in assisted reproduction.