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 ofthe gonadotrophin-releasing hormone (GnRH) agonist, triptorelin acetate,that suppresses the GnRH-induced release of luteinizing hormone (LH) attime of human chorionic gonadotrophin (HCG) injection and thereby preventsspontaneous LH surges during in-vitro fertilization (IVF) stimulationcycles. Therefore, a double-blind, prospective and randomized titrationstudy was performed. A total of 48 IVF patients were divided into fourgroups of 12 patients. Each group received a different dose of triptorelinacetate, namely 5, 15, 50 or 100 microg s.c. daily. Standard ovarianstimulation was carried out using urinary follicle stimulating hormone(FSH) preparations. A 500 microg GnRH test was performed 90 min before theHCG injection in order to measure the degree of pituitary desensitization.Spontaneous LH surges were not detected in any of the groups, althoughthree patients in the 5 microg group had ovulated at the time of ovumretrieval. The pituitary LH response to the GnRH test at time of HCG,expressed as area under the curve (AUC), appeared to be dose-dependent.Thus, a daily s.c. dose of 100 microg triptorelin acetate appears to be toohigh, since adequate desensitization of the pituitary (i.e. no spontaneousLH surge) can be achieved with doses as low as 15 and 50 microg.