PLOD1 and hypogonadotropic hypogonadism: Abnormalities in gonadotropin-releasing hormone (GnRH) secretion (2, 3) result in hypogonadotropic hypogonadism with impaired luteinizing hormone (LH) pulsatile secretion (4–8), and insufficient LH and follicle-stimulating hormone (FSH) concentrations (5, 9) to maintain full folliculogenesis and therefore ovulatory function, and the condition is also referred to as functional hypogonadotropic hypogonadism.