Although first described in the 1980 s,FSH was found to stimulate the ovarian production of an uncharacterized hormone known by its specific effect of reducing pituitary responsiveness to GnRH,named as gonadotropin surge-attenuating factor(GnSAF).People has been proposing that the main role of GnSAF is probably the negative regulation of pulsatile LH secretion as an antagonist of estrogen,mainly elevate during the first half of the follicular phase,and decline before ovulation,indicating a critical role in the regulation of folliculogenesis and oestradiol secretion.Previous studies have revealed that GnSAF only exist in granulose cells of small follicle,stimulated by FSH.The bioactivity of GnSAF is consistent with the diameter of follicle,the highest in 11 mm follicle in stimulating cycles and 6-8 mm follicle in nature cycles.Though to date there have been five main published attempts to characterize GnSAF,yielding amino acid sequences on four occasions,it has still not been convincingly characterized and no published candidate amino acid sequences conclusively relate to GnSAF bioactivity.Because premature luteinization occurs more frequently in older or poor responder patients,defective production of GnSAF may be involved.Our study was to test this phenomenon by adding estrogen in luteal transition phase ahead of IVF/ICSI stimulating cycle,to observe the hormone profile,clinic outcome and probably premature luteinization.The results indicate when FSH level was repressed by estrogen application during the luteal transition phase,more gonadotropin,longer stimulation may be needed,and progesterone rise may result from the premature releasing of LH,that could be a negative affect on GnSAF bioactivity on ovulation.
