title: Testosterone but not estradiol level is positively related to muscle strength and physical performance independent of muscle mass: a cross-sectional study in 1489 older men.
abstract: OBJECTIVE
  To examine the relationship between different measures of testosterone and estradiol (E(2)), muscle mass, muscle strength, and physical performance; and to test whether the association of sex hormone level with muscle strength and physical performance was independent of muscle mass.
  
  
  METHODS
  A cross-sectional survey on 1489 community-dwelling men older than 64 years of age. Serum levels of testosterone and E(2) were measured by mass spectrometry, and sex hormone-binding globulin (SHBG) levels were measured by immunoradioassay. Muscle mass was examined by dual-energy X-ray absorptiometry and physical performance was assessed by hand-grip strength, gait speed, step length and chair-stand test.
  
  
  RESULTS
  Appendicular skeletal mass (ASM) was positively associated with total testosterone (TT; P<0.001), free testosterone (FT; P<0.001), and total E(2) (P<0.001) but not with free E(2) (P=0.102). After adjustment for age, serum SHBG and relative ASM, both TT and FT were significantly associated with grip strength, narrow-walk speed and the composite neuromuscular score. Higher total E(2), but not free E(2) was associated with lower grip strength (P<0.05) after adjustment for age, FT, SHBG and relative ASM.
  
  
  CONCLUSIONS
  Testosterone level was related to both muscle mass, strength and physical performance. Total E(2) level, though related to muscle mass positively, affected muscle strength adversely in older men.
authors.affiliation: The S H Ho Centre of Gerontology and Geriatrics, The Chinese University of Hong Kong, Shatin, Hong Kong, People's Republic of China. auyeungtw@gmail.com
authors.forename: Tung Wai
authors.initials: TW
authors.lastname: Auyeung
authors.forename: Jenny Shun Wah
authors.initials: JS
authors.lastname: Lee
authors.forename: Timothy
authors.initials: T
authors.lastname: Kwok
authors.forename: Jason
authors.initials: J
authors.lastname: Leung
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlsson
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Vandenput
authors.forename: Ping Chung
authors.initials: PC
authors.lastname: Leung
authors.forename: Jean
authors.initials: J
authors.lastname: Woo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D013739:Testosterone / Q000097:blood*
chemical_list: D015415:Biomarkers; D013739:Testosterone; D004958:Estradiol