[Ovarian stimulation: is exogenous LH necessary in all patients?]

FSH and LH play an essential but different role in the growth of ovarian follicles during the cycle. In stimulation protocols, good follicular development is obtained in most patients treated with FSH alone whereas the role of LH is more complex and controversial. Clinical and pre-clinical studies have shown that optimal follicular development is obtain if (i) exposure to endogenous and/or exogenous LH is sufficient ("threshold" concept) and (ii) exposure to LH is not excessive ("ceiling" concept). The recombinant luteinizing hormone (r-hLH, Luveris) is the only available stand-alone preparation of LH. Its characteristics are a high specific activity, the absence of undesirable proteins and an excellent batch to batch consistency. Luveris is indicated in association with FSH for stimulating follicular development in LH and FSH deficient women (defined by an endogenous LH level < 1.2 UI/l). In this subgroup of patients, the therapeutic benefit of exogenous LH at a daily dose of 75 IU is only observed when endogenous serum LH is below than 1.2 IU/l: LH threshold concept. In ART, the combination of exogenous LH at a daily dose from 75 to 150 IU and recombinant FSH improved the ovarian stimulation results only in a minority of patients (5 to 17%). On the opposite, studies conducted in OMS I and II patients showed that high doses of exogenous LH lead to atresia of secondary follicles. So, a daily dose of exogenous LH greater than 225 IU had a deleterious effect on follicular growth: LH ceiling concept.