Relationship between LH and oestradiol in IVF cycles before GnRH antagonist initiation

The objective of this prospective study was to assess the relationship of LH and oestradiol on day 7 of the cycle in patients stimulated with recombinant FSH (rec-FSH) for IVF before initiation of gonadotrophin-releasing hormone (GnRH) antagonist. One hundred and forty-six women treated for IVF using GnRH antagonists for premature LH rise suppression were stimulated with 150 IU of rec-FSH from day 2 to day 6 of the cycle. On cycle day 7, LH concentrations (median 1.8, range 0.1-7.51) were positively associated with oestradiol concentrations on the same day by multiple regression analysis controlling for patient's age, concentrations of FSH and LH on cycle day 2, FSH concentrations on cycle day 7 and follicular index on cycle day 7. In conclusion, the higher the endogenous unsuppressed LH concentrations on day 7 of the cycle after 5 days of stimulation with rec-FSH for IVF, the higher the serum oestradiol concentrations on the same day.