title: Heritability of blood concentrations of sex-steroids in relation to body composition in young adult male siblings.
abstract: OBJECTIVE
  Sex steroid concentrations in men are related to body composition and both are determined by genetic and environmental factors. This study investigates heritability estimates of sex steroid serum concentrations and body composition as well as the genetic and environmental components of their interrelation.
  
  
  METHODS
  Six hundred and seventy-four men (25-45 years) were included in this study with 274 independent pairs of brothers.
  
  
  METHODS
  Body composition and regional fat mass estimates were determined using dual-energy X-ray absorptiometry. Serum testosterone (T), SHBG, oestradiol (E(2)) and LH levels were determined by immunoassay; free T and E(2) levels were calculated.
  
  
  RESULTS
  Both sex steroid hormone concentrations and indices of body composition exhibited significant heritability estimates. Among sex steroid hormones, T had the highest heritability (h(2) = 0.65), followed by free T (h(2) = 0.54). A heritability of 0.73 was observed for SHBG; a heritability estimate of 0.83 was obtained for body weight. Significant genetic correlations were found between whole body fat mass and serum T (rho(G) = -0.46), free T (rho(G) = -0.27) and SHBG (rho(G) = -0.48) concentrations. No genetic relationship was observed between total (F) E(2) or LH concentrations, respectively, and body composition.
  
  
  CONCLUSIONS
  Both sex steroid serum levels and body composition are under strong genetic control. Their interrelation is in part underlied by a genetic correlation, indicative of the action of shared genes.
authors.affiliation: Department of Endocrinology, Ghent University Hospital, Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Bogaert
authors.forename: Youri
authors.initials: Y
authors.lastname: Taes
authors.forename: Peter
authors.initials: P
authors.lastname: Konings
authors.forename: Kristel
authors.initials: K
authors.lastname: Van Steen
authors.forename: Dirk
authors.initials: D
authors.lastname: De Bacquer
authors.forename: Stefan
authors.initials: S
authors.lastname: Goemaere
authors.forename: Hans
authors.initials: H
authors.lastname: Zmierczak
authors.forename: Patricia
authors.initials: P
authors.lastname: Crabbe
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Kaufman
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000328:Adult; D001823:Body Composition / Q000235:genetics*; D015992:Body Mass Index; D016022:Case-Control Studies; D004777:Environment; D012739:Gonadal Steroid Hormones / Q000097:blood* / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D035781:Siblings
chemical_list: D012739:Gonadal Steroid Hormones