title: Short QTc interval in males with klinefelter syndrome-influence of CAG repeat length, body composition, and testosterone replacement therapy.
abstract: BACKGROUND
  Klinefelter syndrome (KS) is a sex chromosomal aneuploidy (47,XXY) affecting 1/660 males. Based on findings in Turner syndrome, we hypothesized that electrocardiogram (ECG) abnormalities would be present in males with KS.
  
  
  OBJECTIVE
  To investigate ECGs in males with KS and compare with controls.
  
  
  METHODS
  Case control study of 62 males with KS and 62 healthy males matched on age. The primary outcome parameter was a difference in the ECG presentation between the two groups. The ECGs were analyzed by one blinded examiner (intraobserver variability 0.2-2.1%). The QT-interval was measured using "teach-the-tangent" method excluding the U-wave. QTc was calculated using Bazett's equation, Hodges' equation, and a linear regression model. Body mass index, abdominal fat, and muscle mass as well as sex hormone levels were secondary parameters. The prevalence of mutations in genes related to short QT syndrome was determined in participants with a QTc < 330 ms.
  
  
  RESULTS
  Compared to controls, the QTc-interval was shorter (P = 0.02-0.06) in males with KS depending on the applied correction method. QTc was shortest among testosterone (T)-treated males with KS, while untreated and thus hypogonadal KS had QTc interval comparable to controls. No mutations in genes related to short QT syndrome were found.
  
  
  CONCLUSIONS
  We found short QTc interval in males with KS, with further shortening of the QTc interval by T. These results suggest that genes on the X chromosome could be involved in regulation of the QTc interval and that T treatment may aggravate this mechanism.
authors.affiliation: Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Inger Norlyk
authors.initials: IN
authors.lastname: Jørgensen
authors.forename: Anne
authors.initials: A
authors.lastname: Skakkebaek
authors.forename: Niels Holmark
authors.initials: NH
authors.lastname: Andersen
authors.forename: Lisbeth Nørum
authors.initials: LN
authors.lastname: Pedersen
authors.forename: David Michael
authors.initials: DM
authors.lastname: Hougaard
authors.forename: Anders
authors.initials: A
authors.lastname: Bojesen
authors.forename: Christian
authors.initials: C
authors.lastname: Trolle
authors.forename: Claus Højbjerg
authors.initials: CH
authors.lastname: Gravholt
mesh_terms: D000328:Adult; D017677:Age Distribution; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology; D001823:Body Composition; D016022:Case-Control Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D004522:Educational Status; D004562:Electrocardiography / Q000706:statistics & numerical data; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D020249:Hormone Replacement Therapy / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D008297:Male; D012307:Risk Factors; D013739:Testosterone / Q000627:therapeutic use*; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*
chemical_list: D013739:Testosterone
keywords: ECG; body composition; cardiology; hypogonadism; hypothalamus-pituitary-testicular axis