title: Testosterone concentrations in young healthy US versus Chinese men.
abstract: BACKGROUND
  Previous small studies examining differences in testosterone concentrations by ethnicity found mixed results for Caucasians and Chinese men, which might be confounded by age differences and living standards. The aim of the present study is to examine the differences in total, free, and bioavailable testosterone concentrations between healthy young men from the United States (US) and from the most economically developed part of China, i.e., Hong Kong (HK).
  
  
  METHODS
  Cross-sectional analysis based on 365 young men from the Third National Health and Nutrition examination Survey (NHANES III) in the US and 299 Chinese men recruited from university students. All participants were aged from 18 to 29 years. Main outcome measures were total testosterone (TT) and calculated bioavailable testosterone (Bio T) and free testosterone (FT).
  
  
  RESULTS
  In both US and Chinese men, TT, FT, and Bio T concentration peaked at 20-24 years of age, at 23.19, 0.49, and 12.23 nmol/l in US men, and 20.72, 0.48 and 12.59 nmol/l in Chinese men, respectively. Among those aged 18-24 years, after adjusting for age, US men had higher TT (mean, 95% confidence interval: 21.64, 21.31-21.99 versus 20.20, 20.12-20.28 nmol/l), but not FT (0.47, 0.47-0.48 versus 0.47, 0.47-0.47 nmol/l) or Bio T (11.90, 11.83-11.97 versus 12.39, 12.35-12.42 nmol/l) than Chinese men.
  
  
  CONCLUSIONS
  TT, but not FT or Bio T concentrations are lower in young healthy Chinese men than US men. These differences apparent in young men may be important in understanding different patterns of diseases between Western and Asian populations.
authors.affiliation: School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, SAR, China.
authors.forename: L
authors.initials: L
authors.lastname: Xu
authors.forename: S L
authors.initials: SL
authors.lastname: Au Yeung
authors.forename: S
authors.initials: S
authors.lastname: Kavikondala
authors.forename: G M
authors.initials: GM
authors.lastname: Leung
authors.forename: C M
authors.initials: CM
authors.lastname: Schooling
mesh_terms: D000293:Adolescent; D000328:Adult; D001682:Biological Availability; D003430:Cross-Sectional Studies; D006723:Hong Kong; D006801:Humans; D008163:Luminescent Measurements; D008297:Male; D009749:Nutrition Surveys; D011863:Radioimmunoassay; D013739:Testosterone / Q000097:blood* / Q000493:pharmacokinetics; D014481:United States; D055815:Young Adult
chemical_list: D013739:Testosterone