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A premature LH surge (trigger to ovulate) may occur during menotropin therapy.
There is apparently a natural substance (not yet identified) that inhibits ovulation during the maturation of eggs. In a natural cycle, the signal from the brain to the ovary to trigger ovulation (the LH surge) appears to occur once the serum estradiol level reaches a certain concentration (about 250 pg/mL) for a certain length of time (about 2 days). In a cycle of controlled ovarian hyperstimulation using menotropins, the serum estradiol level may be greater than 250 pg/mL for much longer than a week without triggering ovulation. Therefore, the existence of a natural “ovulation inhibitor” has been postulated.
In possibly 5-20% (1 in 20 to 1 in 5) of women undergoing menotropin therapy there may be a premature LH surge. If this occurs, the use of a GnRH agonist such as Lupron or Synarel should prevent a spontaneous LH surge (ovulation) in future cycles. These medications (GnRH agonists) suppress the ovaries so that higher dosages of menotropins are usually required to accomplish multiple follicular development.
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