The LH endocrine profile in gonadotropin-releasing hormone analogue cycles

Research question: What does the evolution of serum luteinizing hormone (LH) levels look like throughout the follicular phase of cycles in which gonadotrophins and gonadotropin-releasing hormone (GnRH) analogues in the context of ovarian stimulation for assisted reproduction technologies (ART) were used?Design: This was a retrospective, observational cohort study in a tertiary infertility clinic. 1303 patients aged between 18 and 43 years of age were included with a total of 2200 cycles for ART, using GnRH-analogues for pituitary down-regulation stimulated with human menopausal gonadotropin (hMG) or recombinant follicle stimulating hormone (rec-FSH). Follicular evolution of LH during ovarian stimulation in different treatment protocols was modeled as repeated measures.Results: LH evolution showed a significant decrease in antagonist/hMG cycles of 0.17 IU/L per day (95% CI [-0.20, -0.12]) and 0.26 IU/L per day in rec-FSH cycles (95% CI [-0.29, -0.22]). This decrease was significantly stronger in rec-FSH cycles than in hMG cycles (estimated difference of 0.09 IU/L per day, 95% CI [0.04, 0.15]). Short agonist/hMG cycles showed a significant increase in LH of 0.04 IU/L per day (95% CI [0.01, 0.08]), while the increase of 0.01 IU/L per day in cycles with rec-FSH was not significant (95% CI [-0.08, 0.10]).Conclusion: Follicular evolution of LH during controlled ovarian stimulation differs between different GnRH analogue cycles. A statistically significant decrease in LH was shown in GnRH antagonist cycles being more pronounced with rec-FSH compared to hMG. This decrease in LH in antagonist cycles and the potential impact on estradiol levels and follicle growth needs further examination.