Congenital hypogonadotropic hypogonadism (CHH), includingKallmann syndrome, is frequently genetic, with variants in genes such asFGFR1, ANOS1 and GNRHR. Clinicalassessment includes family history, growth patterns, and red flags such asmicropenis, cryptorchidism or anosmia. This evidence concerns the gene GNRHR and Kallmann syndrome.