Mixed hypogonadism: a neglected combined form of hypogonadism

Purpose Kallmann syndrome is a rare disease characterized by delayed puberty, infertility and anosmia. We report the clinical and genetic characteristics of three patients with Kallmann syndrome who presented with Klinefelter syndrome and defined this neglected combined form of hypogonadism as mixed hypogonadism. Methods Clinical data and examinations were obtained, including laboratory examination and magnetic resonance imagination (MRI) of the olfactory structures. Congenital hypogonadotropic hypogonadism (CHH) related genes were screened by next generation sequencing (NGS). Results Three patients with Kallmann syndrome were included. They had co-existence with Klinefelter syndrome and showed hypogonadotropic hypogonadism. Patient 1 was complicated with germinoma. Conclusion Mixed hypogonadism was defined as hypogonadotropic hypogonadism in Klinefelter syndrome or primary testicular disease. Clinicians should be alert to mixed hypogonadism when spermatogenesis induction failed in patients with CHH or gonadotropin levels decrease in patients with Klinefelter syndrome.