Agonists versus antagonists in COH

Abstract

The gonadotropin-releasing hormone (GnRH) analogs suppress the pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH) secretion and enable the control of ovarian folliculogenesis to yield high pregnancy rates in IVF/ICSI cycles. The GnRH analogs have many advantages such as high potency, increased half life, and increased binding capacity to pituitary GnRH receptors, compared with the GnRH molecule. The two types of GnRH analogs in clinical practice are the GnRH agonist and GnRH antagonist. The effi cacy of these two GnRH analogs is still under debate. Recent studies have failed to reveal the superiority of one molecule over another. In normo-responders, the implantation rate, clinical pregnancy rate, and miscarriage rates were similar in the GnRH antagonist regimens as well in the GnRH agonist long protocol. However, a signifi cantly higher number of oocytes and higher proportion of mature MII oocytes was retrieved per patient randomized in the GnRH agonist group compared to the GnRH antagonist group. In poor responders, the duration of stimulation with the GnRH antagonist was smaller than the GnRH agonist cycle, although there was no statistical difference in the number of oocytes retrieved, the number of mature oocytes retrieved, the cycle cancellation rate, and clinical pregnancy rate between the GnRH antagonist and GnRH agonist protocols.