THE HORMONAL FLARE-UP FOLLOWING GONADOTROPIN-RELEASING-HORMONE AGONIST ADMINISTRATION IS INFLUENCED BY A PROGESTOGEN PRETREATMENT

In a short-term protocol, the influence of progestogen pretreatment up on the oestradiol flare-up (Delta E2) induced by gonadotrophin-releasi ng hormone agonist (GnRHa) was assessed in relation to in-vitro fertil ization (IVF) outcome in 90 cycles programmed (It = 52) or not (n = 38 ) by norethisterone (10 mg/day for 12-20 days), Patients pretreated by progestogen had a significantly lower Delta E2 value than patients wi thout pretreatment (Delta E2 = 26 +/- 5 versus 61 +/- 8 pg/ml, P = 0.0 03), It could be related to a lower gonadotrophic response for luteini zing hormone (LH) (Delta LH = 9 +/- 0.8 versus 14.5 +/- 2.2 IU/l, P = 0.01), The IVF outcome (final oestradiol, number of oocytes or embryos ) was similar in both groups and Delta E2 was well correlated with the se final parameters in each group. A significant rise in serum progest erone was observed only in patients without pretreatment (Delta P = 1. 1 +/- 0.2 versus 0.1 +/- 0.1 ng/ml, P < 0.0001), Thus norethisterone p retreatment decreases the oestradiol flare-up and prevents the early i ncrease of progesterone (by avoiding some rescue of the corpus luteum or some luteinization of small developing follicles) but does not infl uence the outcome of the IVF cycle, In clinical practice, evaluation o f the hormonal flare-up for predicting IVF outcome must take into acco unt any pretreatment prescription.