To add or not to add LH: comments on a recent commentary.

From a period of time when LH activity supplementation in stimulation protocols for assisted reproductive technology was questioned, recent scientific evidence seems to prove a role of LH activity in optimizing the clinical results of certain subgroups. Until now, apart from the hypogonadotrophic hypogonadal patient, two subgroups of patients have attracted attention: patients over 35 years of age, and normogonadotrophic patients with an initial low response to recombinant FSH (rFSH). However, in a recent paper, another subgroup of patients has been identified: normogonadotrophic patients with high endogenous LH levels (>1.99 IU/l) on day 8 of stimulation after a long GnRH agonist down-regulation. By adding recombinant LH (rLH) from day 8 to the stimulation protocol, this subgroup of patients achieved good implantation rates, similar to those of patients with lower LH levels. Interestingly, the dynamics of the endogenous LH levels during down-regulation in this group of patients differed from those of patients with lower LH levels. The immunoreactivity of the LH molecule does not necessarily reflect the bioactivity, which might explain the beneficial effect of LH activity supplementation in patients with high endogenous LH levels after down-regulation. Future studies should be focused on subgroups to further explore the effect of LH activity supplementation in assisted reproduction techniques.