title: Associations of endogenous testosterone and SHBG with glycated haemoglobin in middle-aged and older men.
abstract: OBJECTIVE
  Low circulating levels of testosterone and sex-hormone-binding globulin (SHBG) are associated with increased cardiovascular risk in men. This association may be partially mediated through changes in glucose metabolism, but relatively few data are available on the relationship between sex hormones and markers of long-term glycaemia. We assessed the associations of endogenous testosterone and SHBG with glycated haemoglobin (HbA(1c) ) in men.
  
  
  METHODS
  Cross-sectional study of 1292 men from the Norfolk population of European Prospective Investigation into Cancer (EPIC-Norfolk).
  
  
  METHODS
  Glycated haemoglobin, total testosterone (TT) and SHBG levels were measured, and free testosterone (FT) levels were calculated. Multiple linear regression models were used to assess the associations of TT, SHBG and FT with HbA(1c).
  
  
  RESULTS
  Men with diabetes had lower testosterone and SHBG levels. In non-diabetic men, HbA(1c) levels were inversely associated with TT and calculated FT independently of age, body mass index, smoking, alcohol consumption and physical activity. The adjusted change in HbA(1c) was 0·055 (95% CI 0·025; 0·085) per standard deviation (SD) decrease in TT and 0·041 (95% CI 0·010; 0·073) per SD decrease in calculated FT, respectively. SHBG levels were inversely associated with HbA(1c) after multivariable adjustment (β = 0·038 per SD decrease (95% CI 0·004; 0·071)).
  
  
  CONCLUSIONS
  In middle-aged and older men, low endogenous testosterone and SHBG levels are associated with glycaemia, even below the threshold for diabetes. Further studies are needed to determine the effects of interventions that raise testosterone levels in men having increased HbA(1c) and subnormal testosterone levels.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands. j.s.m.brand-3@umcutrecht.nl
authors.forename: Judith S
authors.initials: JS
authors.lastname: Brand
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wareham
authors.forename: Mitch
authors.initials: M
authors.lastname: Dowsett
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Folkerd
authors.forename: Yvonne T
authors.initials: YT
authors.lastname: van der Schouw
authors.forename: Robert N
authors.initials: RN
authors.lastname: Luben
authors.forename: Kay-Tee
authors.initials: KT
authors.lastname: Khaw
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases; D003430:Cross-Sectional Studies; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007003:Hypoglycemia / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012738:Sex Hormone-Binding Globulin / Q000032:analysis*; D013739:Testosterone / Q000097:blood*
chemical_list: D006442:Glycated Hemoglobin; D012738:Sex Hormone-Binding Globulin; D013739:Testosterone