Effects of gonadotrophin-releasing hormone agonists (GnRHa) on follicle and oocyte quality.

This review summarizes the main clinical and research studies on direct and indirect effects of gonadotrophin-releasing hormone agonists (GnRHa) on follicles and oocytes in animals and humans. There is evidence for extra-pituitary actions of GnRHa, especially on follicle growth, follicular steroidogenesis, and oocyte meiotic maturation. Different effects have been reported from using various GnRHa molecules. However, a direct effect of GnRHa on oocyte quality in gonadotrophin stimulated cycles has not yet been demonstrated. Observed high pregnancy rates per ovarian puncture in in-vitro fertilization cycles using GnRHa, at least in long protocols, might result from higher numbers of oocytes recovered following administration of large doses of gonadotrophins, despite the fact that these oocytes may have a lower ability to fertilize and grow. Although there are obvious clinical advantages of using GnRHa for ovarian stimulation, more studies are needed to clarify the effects of these treatments at ovarian and uterine levels.