GnRH Agonist Triggering

The use of gonadotropin releasing hormone agonist (GnRHa) has been used as a substitute to human chorionic gonadotropin (hCG) for the induction of oocyte maturation and prevention of ovarian hyperstimulation syndrome (OHSS) during IVF cycles. A single bolus of GnRHa will cause the endogenous release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which resembles the natural mid-cycle surge of gonadotropins seen shortly before ovulation, and thus a bolus of GnRHa can “trigger” ovulation. The shortened LH surge after GnRHa trigger is sufficient to induce maturation of oocytes but not to maintain adequate corpora lutea to resemble a natural luteal phase. In recent years, the administration of human chorionic gonadotropin (hCG) at the time of GnRHa trigger or at the time of oocyte retrieval has demonstrated that high pregnancy rates can be achieved while maintaining low rates of ovarian hyperstimulation syndrome (OHSS). Another successful strategy to achieve live births following GnRHa trigger is intensive luteal support with oestrogen and progesterone. GnRHa trigger has revolutionized the practice of assisted reproductive technology by nearly eliminating the risk of OHSS and has been used widely in freeze-all cycles. Future research directions include optimizing the dose and timing of GnRHa administration.