title: Low body mass index and declining sex steroids explain most age-related bone loss in Brazilian men.
abstract: CONCLUSIONS
  Osteoporosis in men is underestimated, but our data point to an increasing prevalence rate in those over 70 years old with body mass index (BMI) <25 kg/m(2), bioavailable testosterone <2.7 nmol/L, bioavailable estradiol <40 pmol/L, and high bone turnover, defined in this study as serum carboxyterminal cross-linked telopeptide of type I collagen (ICTP) >4.3 microg/L.
  
  
  BACKGROUND
  The association of sex steroids and osteoporosis was evaluated in 104 men, aged 50-93 years old.
  
  
  METHODS
  Bone mineral density (BMD), bone turnover (ICTP), testosterone (T), and estradiol (E(2)) were measured; free and bioavailable hormones (free testosterone index [FTI], BioT, free estradiol index [FEI], and BioE(2)) were calculated from T, E(2), sex hormone-binding globulin (SHBG), and albumin. Nonparametric analysis and Poisson regression models were used.
  
  
  RESULTS
  Significant increases in SHBG and ICTP and decreases in femoral neck BMD, FTI, FEI, BioT, and BioE(2) were observed with each additional decade of age. Femoral neck BMD was inversely correlated with ICTP, and both were significantly associated with SHBG, FTI, BioT, FEI, and BioE. There was a direct and graded association between age and osteoporosis prevalence rate (OP PR; p = 0.028). Compared to participants less than 70 years old, the crude OP PR of those 80 years and older was 3.2 (95%CI = 1.4-7.3). Adjusting sequentially for BMI and bioavailable sex hormones attenuated the association between age and osteoporosis prevalence by 55% and 77%, respectively.
  
  
  CONCLUSIONS
  Our data support the view that low BMI and declining sex steroids explain most of the association between aging, increased bone turnover, and osteoporosis in men.
authors.affiliation: Department of Internal Medicine, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: R F
authors.initials: RF
authors.lastname: Lopes
authors.forename: S A G J
authors.initials: SA
authors.lastname: Ferreira
authors.forename: C M
authors.initials: CM
authors.lastname: Coeli
authors.forename: M L F
authors.initials: ML
authors.lastname: Farias
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood; D000418:Albumins / Q000378:metabolism; D015992:Body Mass Index; D015519:Bone Density; D001938:Brazil; D024042:Collagen Type I; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood*; D005272:Femur Neck / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood* / Q000209:etiology; D010446:Peptide Fragments / Q000097:blood*; D010455:Peptides; D011347:Procollagen / Q000097:blood*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013739:Testosterone / Q000097:blood*
chemical_list: D000418:Albumins; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; D012738:Sex Hormone-Binding Globulin; C052929:collagen type I trimeric cross-linked peptide; D013739:Testosterone; D004958:Estradiol