title: Increased plasma osteoprotegerin concentrations are associated with indices of bone strength of the hip.
abstract: OBJECTIVE
  Osteoprotegerin (OPG) is an important regulator of bone turnover through its effects on osteoclastogenesis, yet findings from previous studies of circulating OPG and commonly measured bone indices in humans have been conflicting. We conducted a cross-sectional study to evaluate the association between plasma OPG and femoral neck (FN) bone density (BMD) and geometry in a large cohort of women and men.
  
  
  METHODS
  Participants included 1379 postmenopausal women and 1165 men, aged 50-89 yr (mean, 64 yr), in the Framingham Offspring Study. Dual x-ray absorptiometry was used to evaluate FN BMD and geometry (bone width, section modulus, and cross-sectional area at the narrow neck region). Plasma OPG concentrations were measured by ELISA. Sex-specific analysis of covariance was used to calculate means and assess linear trend in BMD and geometry values across OPG quartiles, adjusted for confounders.
  
  
  RESULTS
  OPG concentrations were greater in women than men, increased with age, and were greater in smokers and those with diabetes and heart disease. Multivariable-adjusted mean FN BMD in women increased from the lowest to the highest OPG quartile (trend, P < 0.01). However, no linear trend between FN BMD and OPG was observed in men (trend, P = 0.34). Section modulus and bone width increased with OPG in men (trend, P < 0.01), whereas no association between hip geometry indices and OPG was observed in women.
  
  
  CONCLUSIONS
  Higher OPG concentration may indicate greater skeletal strength in women and men, possibly through reducing bone loss in women and increasing periosteal apposition in men.
authors.affiliation: Institute for Aging Research, Hebrew SeniorLife, 1200 Centre Street, Boston, MA 02131, USA. samelson@hrca.harvard.edu
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Samelson
authors.forename: Kerry E
authors.initials: KE
authors.lastname: Broe
authors.forename: Serkalem
authors.initials: S
authors.lastname: Demissie
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Beck
authors.forename: David
authors.initials: D
authors.lastname: Karasik
authors.forename: Sekar
authors.initials: S
authors.lastname: Kathiresan
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Kiel
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D005260:Female; D005272:Femur Neck / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin / Q000097:blood*; D053245:RANK Ligand / Q000097:blood
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; C505688:TNFSF11 protein, human