LH in the follicular phase: neither too high nor too low.

The role of LH in the natural menstrual cycle is not disputed. However, there are a variety of opinions regarding the potential role of exogenous LH in ovulation induction and whether it is actually needed. Recent years have seen renewed interest in this issue for several reasons. First, ovulation-inducing drugs are increasingly being administered to normally ovulating women. Second, recombinant human FSH products completely devoid of LH activity are now available. Third, gonadotrophin-releasing hormone (GnRH) analogues (agonists and antagonists) prevent the untimely LH surge but also suppress endogenous LH activity during the follicular phase. This review analyses whether or not all patients need LH for follicular growth stimulation and new opportunities for improved treatment as a result of the availability of recombinant human LH both in patients with ovulatory disorders (World Health Organization (WHO) groups I and II anovulatory patients) and those undergoing multiple follicular development for assisted reproduction.