In a cohort of adolescents and adults with PWS, we characterized four distinct patterns of gonadal dysfunction based on FSH and inhibin B levels: hypergonadotrophic (primary gonadal) hypogonadism, hypogonadotrophic (central/hypothalamic) hypogonadism, partial gonadal and central dysfunction and mild central with severe gonadal dysfunction. The gene discussed is BRD2; the disease is Prader-Willi syndrome.