The use of an ag-GnRH analogue, namely triptorrelin acetate, can be used both in antagonist stimulation protocols, instead of the conventional hCG,( 25 ) and in COS protocols with oral progestin, with good response in oocyte quality.( 27 ) Ag-GnRH has a shorter half-life and a lower incidence of OHSS when compared to hCG to induce ovulation. The gene discussed is GNRH1; the disease is ovarian hyperstimulation syndrome.