GnRH antagonists in ART: lower embryo implantation?

Recently, concerns have been raised regarding possible adverse effects of g onadotrophin-releasing hormone (GnRH) antagonists on extra-pituitary reprod uctive cells and organs, i.e. ovarian cells, oocyte, embryo, endometrium, T hese concerns are based on numerous in-vitro studies suggesting decreased b iosysnthesis of growth factors caused by local action of GnRH antagonists, Clinically, it has been shown that the use of high doses (II mg daily) of G nRH antagonists is associated with low implantation rates in IVF, Although such direct adverse effect of GnRH antagonists cannot be ruled out at this time, so far clinical experience points to profound LH suppression as the m ajor caveat associated with the use of high doses of GnRH antagonists. Very low LH concentrations are associated with aberrant concentrations of oestr adiol during ovarian stimulation, which may in turn adversely effect implan tation potential. The clinical data available thus far on the use of GnRH a ntagonists originate from protocols designed for clinical studies. It is pr edicted that as more clinical experience is gained, and with protocol modif ications to suit individual patient response, GnRH antagonists will be comp arable with the agonists in terms of cycle outcome.