Women with poor response to IVF have lowered circulating gonadotrophin surge-attenuating factor (GnSAF) bioactivity during spontaneous and stimulated cycles

BACKGROUND: Up to 13% of IVF cancellations are due to poor responses during down-regulated cycles. Because premature luteinization occurs more frequently in older or 'poor responder' patients, defective production of gonadotrophin surge-attenuating factor (GnSAF) may be involved. METHODS: Nine women with normal previous IVF response (NORM) and 9 with previous poor IVF response (POOR) were monitored in a spontaneous cycle (blood samples: days 2, 7, 11, 15 and 20) and then stimulated with recombinant human FSH (rFSH) under GnRH agonist (blood samples: treatment days GnRH agonist + 2, GnRH agonist + 7, day of HCG administration and days HCG + 1 and HCG + 8). LH, FSH, estradiol, progesterone and inhibin-A and -B were assayed in individual samples while GnSAF bioactivity was determined in samples pooled according to day, cycle and IVF response. RESULTS: During spontaneous cycles LH, steroids and inhibins were similar between NORM and POOR women, FSH was elevated in POOR women (4.9 +/- 0.3 versus 6.7 +/- 0.6 mIU/l, P < 0.01) and GnSAF bioactivity was detectable on days 2, 7 and 11 in NORM women only. During IVF cycles inhibin-A and -B rose more markedly in NORM than POOR women. Similarly GnSAF production peaked on day GnRH agonist + 7 in NORM women, but on the day of HCG administration in POOR women. CONCLUSIONS: Defects in ovarian responsiveness to FSH include reduced GnSAF production. This suggests that GnSAF should be investigated as a marker of ovarian reserve once an immunoassay becomes available.