According to current thinking, patient subpopulations that may benefit from real LH supplementation include patients with hypogonadotrophic hypogonadism, patients who have profound LH suppression in a long GnRH agonist protocol, patients with a suboptimal response to FSH alone (9–25% of patients) and some patients older than 35 years. This evidence concerns the gene GNRH1 and hypogonadotropic hypogonadism.