title: Serum osteoprotegerin and its relationship with bone mineral density and markers of bone turnover.
abstract: BACKGROUND
  The purpose of this study was to compare age-related differences in osteoprotegerin (OPG) in relationship with BMD and the serum bone markers osteocalcin (OC), collagen crosslinks (CTX), and tartrate-resistant acid phosphatase 5b (TRACP-5b).
  
  
  METHODS
  Data were derived from a cross-sectional study on bone health in a random sample of community-dwelling adults aged 30 to 85 years in the Reykjavik area in Iceland. All subjects had whole body, hip, and lumbar spine BMD measured (by DXA), gave blood samples, and answered a thorough questionnaire on medications and medical history. We assessed relationships using the Spearman correlation coefficient, partial correlation, and multivariable linear regression. Men and women were analyzed separately.
  
  
  RESULTS
  Of 2,310 subjects invited over 2 years, 1,630 participated. After excluding individuals with diseases and medications affecting bone metabolism, 517 women (age 56.1 +/- 16.9 years) and 491 men (age 58.7 +/- 14.9 years) remained for analysis. OPG increased steadily with age in both genders without a gender difference. In women, BMD at all sites declined steadily after age 50. In men, BMD remained relatively stable until age 70, after which it declined significantly. After controlling for age, BMI, and other confounding variables, OPG showed only a borderline positive relationship with whole body BMD in men (P = 0.10), but the relationship was nonsignificant in women. In multivariable models, OPG was inversely related to TRACP-5b (P = 0.002) and positively with OC (P = 0.007), the OC/TRACP-5b (P = 0.001) and OC/CTX (P = 0.02) ratios in women. Among men, multivariable models showed a positive association between OPG and OC (P = 0.05) and OC/TRACP-5b (P < 0.009).
  
  
  CONCLUSIONS
  We conclude that serum OPG levels are associated with a profile of bone turnover markers favoring bone formation, suggesting that OPG may be protective against age-related bone loss. Longitudinal studies are needed to address that issue.
authors.affiliation: Department of Medicine, Landspitali-University Hospital, Reykjavik, Iceland.
authors.forename: Olafur S
authors.initials: OS
authors.lastname: Indridason
authors.forename: Leifur
authors.initials: L
authors.lastname: Franzson
authors.forename: Gunnar
authors.initials: G
authors.lastname: Sigurdsson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006023:Glycoproteins / Q000097:blood*; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin; D018160:Receptors, Cytoplasmic and Nuclear / Q000097:blood*; D018124:Receptors, Tumor Necrosis Factor / Q000097:blood*; D012727:Sex Characteristics
chemical_list: D015415:Biomarkers; D006023:Glycoproteins; D053244:Osteoprotegerin; D018160:Receptors, Cytoplasmic and Nuclear; D018124:Receptors, Tumor Necrosis Factor; C506030:TNFRSF11B protein, human