The role of luteinizing hormone activity in controlled ovarian stimulation

The role of LH in the natural menstrual cycle is undisputed. The active participation of LH in both steroidogenesis and ovulation is well established, but its potential effect on oocyte maturation in the issue of assisted reproduction protocols remains a topic of debate. Although several studies have added to our understanding of the specific actions of androgens in human follicular development, some discrepancies persist regarding their role in oocyte atresia. Clinical situations, where LH is either decreased or absent (e.g. in women with hypogonadotrophic hypogonadism or LH-receptor gene mutations), provide important data supporting the necessity for a minimal amount of LH to evoke ovulation. Recent use of GnRH antagonists, which results in profound suppression of LH concentration, in combination with the pharmacological production of recombinant gonadotrophins, has attracted the attention of investigators. Identification of sub-fertilized women, in whom LH administration could be beneficial and should be indicated, is arousing ever more interest. Based on the available data in the literature, the aims of this review are to assess the role of both endogenous and exogenous LH activity in stimulated cycles, and to evaluate the effects of recombinant human LH supplementation on the ovarian hormonal milieu and on the main outcomes of controlled stimulated cycles.