Gonadotrophin-releasing hormone agonist dose-dependency of pituitary desensitization during controlled ovarian hyperstimulation in IVF

The aim of this study was to find the minimal effective daily s.c. dose of the gonadotrophin-releasing hormone (GnRH) agonist, triptorelin acetate, th at suppresses the GnRH-induced release of luteinizing hormone (LH) at time of human chorionic gonadotrophin (HCG) injection and thereby prevents spont aneous LH surges during in-vitro fertilization (IVF) stimulation cycles. Th erefore, a double-blind, prospective and randomized titration study was per formed, A total of 48 IVF patients were divided into four groups of 12 pati ents, Each group received a different dose of triptorelin acetate, namely 5 , 15, 50 or 100 mu g s.c. daily. Standard ovarian stimulation was carried o ut using urinary follicle stimulating hormone (FSH) preparations, A 500 mu g GnRH test was performed 90 min before the HCG injection in order to measu re the degree of pituitary desensitization. Spontaneous LH surges were not detected in any of the groups, although three patients in the 5 mu g group had ovulated at the time of ovum retrieval. The pituitary LH response to th e GnRH test at time of HCG, expressed as area under the curve (AUC), appear ed to be dose-dependent. Thus, a daily s.c. dose of 100 mu g triptorelin ac etate appears to be too high, since adequate desensitization of the pituita ry (i.e. no spontaneous LH surge) can be achieved with doses as low as 15 a nd 50 mu g.