LH (as HCG) and FSH surges for final oocyte maturation: sometimes it takes two to tango?

Until now, clinicians have been relying solely on LH activity-dependent triggering of final oocyte maturation and thus taken it for granted that the natural midcycle FSH surge is biologically redundant. However, it is time to question this paradigm. Evidence from clinical studies hint that in a yet-to-be-defined subset of patients, dual LH and FSH surge is advantageous compared with LH-only surge in the form of human chorionic gonadotrophin (HCG) trigger. Dual surge can be triggered by a bolus of gonadotrophin-releasing hormone agonist causing a flare-up of both endogenous LH and FSH, resembling the natural midcycle surge of gonadotrophins. HCG given in parallel secures adequate exposure to LH activity. Further research is needed to characterize the patients in whom FSH surge is needed for proper resumption of the oocyte meiotic process.