Follicular and endocrine profiles associated with different GnRH-antagonist regimens: a randomized controlled trial

This trial assessed the impact of early initiation of gonadotrophin-releasing hormone (GnRH) antagonist on follicular and endocrine profiles compared with the fixed GnRH-antagonist protocol. Eighty-five oocyte donors were randomized to GnRH antagonist starting in the mid-luteal phase of the prestimulation cycle (degarelix-ML group), on stimulation day 1 (early follicular phase, degarelix-EF group) or day 6 (fixed protocol) (mid-follicular phase, ganirelix-MF group). Subjects in the degarelix-EF and ganirelix-MF groups received placebo in the prestimulation cycle. At start of stimulation, serum concentrations of FSH (4.6 ± 2.3 versus 6.0 ± 1.8IU/l), LH (2.7 ± 1.4 versus 4.7 ± 1.9IU/l) and oestradiol (87 ± 35 versus 129 ± 50pmol/l) were markedly lower (P<0.001) in the degarelix-ML group than in the placebo group. The coefficients of variation of follicle size (36.7 ± 5.5% versus 39.2 ± 9.4%) were not significantly different. No differences in endometrial histology, embryo quality and pregnancy rates in recipient cycles were observed between the regimens. In conclusion, early administration of GnRH antagonist altered the endocrine profile without modifying the follicular synchrony for the majority of subjects. Whether patients with a more heterogeneous follicle size at start of stimulation may benefit from an earlier intervention remains to be proven.