title: New approaches to the Klinefelter syndrome.
abstract: The Klinefelter syndrome (KS), with an incidence of 1 to 2 per 1000 male neonates, is one of the most frequent congenital chromosome disorders. The 47,XXY karyotype causes infertility, testosterone deficiency and a spectrum of further symptoms and comorbidities. In recent years, significant progress has been made in the elucidation of the pathophysiology and the treatment of the KS. It became clear that, to a large extent, the clinical picture is determined by gene dosage effects of the supernumerary X-chromosome. The origin of the extra X-chromosome from either the father or the mother influences behavioural features of patients with KS. The CAGn polymorphism of the androgen receptor, located on the X-chromosome, has a distinct impact on the KS phenotype. KS predisposes to the metabolic syndrome and its cardiovascular sequelae, contributing to the increased mortality of patients with KS. Neuroimaging studies have correlated anomalies in brain structures with psychosocial problems. The unexpected possibility to produce pregnancies and live birth with either ejaculated sperm--about 8% of KS men have a few sperm in semen--or with sperm extracted from individual tubules obtained by testicular biopsy can be considered a breakthrough. Testosterone substitution requires further optimisation in terms of when to initiate therapy and which preparations and dosages to use. Recently developed animal models help to further elucidation the genetic and pathophysiological basis and may lead to new therapeutic approaches to KS.
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Münster, D-48129 Münster, Germany; Center of Excellence in Genomic Medicine Research, King Abdulaziz University, Jeddah, Saudi Arabia. Electronic address: eberhard.nieschlag@ukmuenster.de.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Nieschlag
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Münster, D-48129 Münster, Germany.
authors.forename: Steffi
authors.initials: S
authors.lastname: Werler
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Münster, D-48129 Münster, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Wistuba
authors.affiliation: Centre of Reproductive Medicine and Andrology, University of Münster, D-48129 Münster, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Zitzmann
mesh_terms: D000818:Animals; D041321:Chromosomes, Human, X; D004195:Disease Models, Animal; D018392:Genomic Imprinting; D020249:Hormone Replacement Therapy; D006801:Humans; D007006:Hypogonadism / Q000235:genetics / Q000523:psychology; D007713:Klinefelter Syndrome / Q000188:drug therapy* / Q000235:genetics / Q000503:physiopathology / Q000523:psychology; D008297:Male; D051379:Mice; D009845:Oligospermia / Q000209:etiology / Q000628:therapy; D010641:Phenotype; D062085:RNA, Long Noncoding / Q000096:biosynthesis / Q000235:genetics; D011944:Receptors, Androgen / Q000235:genetics; D027724:Reproductive Techniques, Assisted; D013739:Testosterone / Q000172:deficiency / Q000627:therapeutic use*
chemical_list: D062085:RNA, Long Noncoding; D011944:Receptors, Androgen; C077885:XIST non-coding RNA; D013739:Testosterone
keywords: 47,XXY karyotype; Klinefelter