Exogenous luteinizing hormone supplementation in controlled ovarian stimulation: why, when and to whom?

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) play an important role in assisted reproductive technol- ogy during ovarian stimulation1. These hormones execute dif- ferent but complementary functions in the control of ovarian folliculogenesis and steroidogenesis but, while the role of FSH is well understood, the need for LH supplementation in controlled ovarian stimulation (COS) is still debated and con- troversial. Several confounding factors (e.g. different exogen- ous LH formulations, different stimulation protocols, different study populations, difficulty in identifying a threshold value below which an LH add-back could be beneficial) contribute to the continuing uncertainty reported in the literature con- cerning exogenous LH supplementation, despite the large number of trials that have been published.