Table 1 Advantages and disadvantages of GnRH agonist protocols and GnRH antagonist protocols
From: GnRH agonist versus GnRH antagonist in in vitro fertilization and embryo transfer (IVF/ET)
GnRH Agonist long | GnRH Antagonist fixed | GnRH Antagonist flexible | GnRH agonist short and ultra-short | |
|---|---|---|---|---|
Advantages | A. Stable and low LH and P levels throughout the stimulation phase B. Suppression of endogenous FSH levels leading to a follicular cohort of all small follilcles at the initiation of FSH stimulation resulting in a synchronized follicular development | A. Immediate, reversible suppression of gonadotropin secretion which avoids effects related to the initial flare up and subsequent down regulation B. Initiation of the IVF treatment in a normal menstrual cycle C. Endogenous inter-cycle FSH rise rather than FSH suppression, thus resulting in a significant reduction in the effective dosage and shorter treatment, than with GnRHa | A. Reduced dose of the antagonist is needed B. The cohort of follicles have more time to develop thus leading to a higher number of follicles in mid-follicular phase | A.The ovarian suppression is not excessive B. The initial stimulation of the GnRH receptors and consequent secretion of endogenous gonadotropins enhance the effects of the exogenously administered gonadotropins |
Disadvantagess | A. More time counsuming and complex stimulation protocols B. Acute stimulation of gonadotropins and steroid hormones due to the flare up effects C. Profound hypoestrogenemia due to downregulation D. Risk of complications (OHSS) | High intercycle endogenous FSH concentrations inducing secondary follicle recruitment and leading to an asynchronous follicular development | LH levels remain unsuppressed during the early follicular phase and enhance E2 production | Flare up effects in mid- follicular phase |
Clinical comments | A. Increased number of oocytes collected B. Additional pregnancy chances from cryo-preserved embryos C. Improvement in routine patient treatment schedule | A. More IVF cycles to be carried out in a given period B. Starting stimulation in patient scheduled for antineoplastic treatments (oocyte cryopreservation) | It makes feasible to tailor stimulation to patients’ needs | A. A microdose GnRHa flare protocol is useful in poor responders B. Several microdoses of GnRHa in the flare up protocols have been tested to achieve gonadotropin release and avoid side-effects of the classic flare up protocol |