title: Sex hormone-binding globulin at the crossroad of body composition, somatotropic axis and insulin/glucose homeostasis in young healthy men.
abstract: OBJECTIVE
  Sex hormone-binding globulin (SHBG) modulates the bioavailability of sex steroids at tissue level. Genetic, hormonal and lifestyle-related factors determine the SHBG levels, and low SHBG levels are a known risk factor for the development of the metabolic syndrome, diabetes and cardiovascular diseases. We investigated to what extent different determinants contribute to the variation in SHBG levels in healthy young men.
  
  
  METHODS
  Healthy male siblings (n = 677) aged 25-45 year were recruited in a cross-sectional, population-based study.
  
  
  METHODS
  Lean and fat mass were measured using dual-energy X-ray absorptiometry (DXA), and immunoassays were used to determine the serum hormonal levels. Additional information about smoking and physical activity was obtained using questionnaires. Carriers of two SHBG polymorphisms, the Asp327Asn polymorphism and the (TAAAA)(n) repeat polymorphism, were identified.
  
  
  RESULTS
  Weight, BMI, whole body fat mass and truncal fat mass were negatively associated with SHBG levels. Body composition characteristics did not differ between SHBG genotype groups, indicating that body composition controls SHBG levels rather than the other way around. The associations may be mediated by adipokines because leptin and adiponectin were, respectively, inversely and positively associated with SHBG levels. Insulin and glucose were negatively associated with SHBG levels, as well as IGF-1 and IGF-BP3, while no associations were found with free thyroid hormone status.
  
  
  CONCLUSIONS
  In conclusion, we found that fat mass, insulin and IGF-1 levels are important negative determinants of SHBG levels in young healthy men. The association with fat mass could be mediated by the effects of adiponectin and/or leptin on SHBG synthesis.
authors.affiliation: Department of Endocrinology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Griet
authors.initials: G
authors.lastname: Vanbillemont
authors.forename: Bruno
authors.initials: B
authors.lastname: Lapauw
authors.forename: Hélène
authors.initials: H
authors.lastname: De Naeyer
authors.forename: Greet
authors.initials: G
authors.lastname: Roef
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Kaufman
authors.forename: Youri E C
authors.initials: YE
authors.lastname: Taes
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D003430:Cross-Sectional Studies; D005786:Gene Expression Regulation; D006706:Homeostasis; D019382:Human Growth Hormone / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D007328:Insulin; D012738:Sex Hormone-Binding Globulin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I