title: IGF-I and testosterone levels as predictors of bone mineral density in healthy, community-dwelling men.
abstract: OBJECTIVE
  Age-related decline in IGF-I and gonadal hormones have been postulated to play an important role in the pathogenesis of age-related bone loss in men. In this cross-sectional study, the relation between serum IGF-I and gonadal hormones with bone mineral density (BMD) was examined in community-dwelling men.
  
  
  METHODS
  Serum IGF-I, testosterone and BMD were examined in 61 community-dwelling men over the age of 27, who were randomly selected from the Calgary cohort of 1000 subjects in the Canadian Multicentre Osteoporosis Study. In the present study, IGF-I, serum testosterone, SHBG, free androgen index (FAI), parathyroid hormone (PTH), 25-hydroxy-vitamin D [25(OH)D] and other markers of bone turnover were measured. BMD was measured at the spine and hip (HOLOGIC 4500). Simple linear regression was used to assess the linear relation between IGF-I, testosterone, BMD and other biochemical markers of bone metabolism and potential confounding variables and subsequent multivariate regression models were constructed separately for each BMD measurement to assess the importance of IGF-I and testosterone in the presence of potential confounding variables.
  
  
  RESULTS
  Serum IGF-I, FAI and SHBG significantly decreased as a function of age, whereas serum levels of PTH increased. Only 25(OH)D, total testosterone and FAI were positively associated with serum IGF-I after adjusting for age and BMI. Multiple linear regression models revealed that IGF-I was a significant predictor of BMD at the total hip, femoral neck and femoral trochanter neck (P < or = 0.001). In contrast, the FAI was a significant predictor of BMD at the lumbar spine and wards area (P < or = 0.011), and SHBG was a significant predictor at the total hip and femoral trochanter (P < or = 0.045).
  
  
  CONCLUSIONS
  These data support the hypothesis that the age-related decline in bone mass in men is associated with declining levels of IGF-I and testosterone.
authors.affiliation: Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Diana
authors.initials: D
authors.lastname: Rucker
authors.forename: Shereen
authors.initials: S
authors.lastname: Ezzat
authors.forename: Anastasia
authors.initials: A
authors.lastname: Diamandi
authors.forename: Javad
authors.initials: J
authors.lastname: Khosravi
authors.forename: David A
authors.initials: DA
authors.lastname: Hanley
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000728:Androgens / Q000097:blood; D015415:Biomarkers / Q000097:blood; D015519:Bone Density; D016723:Bone Remodeling; D002170:Canada; D003430:Cross-Sectional Studies; D006306:Health Surveys; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010024:Osteoporosis / Q000097:blood*; D010281:Parathyroid Hormone / Q000097:blood; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013739:Testosterone / Q000097:blood*
chemical_list: D000728:Androgens; D015415:Biomarkers; D010281:Parathyroid Hormone; D012738:Sex Hormone-Binding Globulin; D015652:25-Hydroxyvitamin D 2; D013739:Testosterone; D007334:Insulin-Like Growth Factor I