Cortical Bone Status Is Associated with Serum Osteoprotegerin Concentration in Men: The STRAMBO Study

Abstract

Osteoprotegerin (OPG) is an inhibitor of bone resorption, but its relationship to bone microarchitecture remains unclear. Our objective was to study the relationship between OPG concentration and bone microarchitecture in men. We conducted a cross-sectional study of a population-based cohort of 1149 men aged 20-87 yr. We assessed bone microarchitecture at the distal radius and tibia by high-resolution peripheral quantitative computed tomography (XtremeCT Scanco) and measured serum OPG concentration and bone turnover markers: osteocalcin, bone-specific alkaline phosphatase, N-terminal extension type I collagen propeptide, C-terminal type 1 collagen telopeptide, and urinary deoxypyridinoline. Differences were assessed in bone microarchitectural parameters across the OPG quartiles in the models adjusted for age, weight, height, physical activity, ischemic heart disease, diabetes mellitus, calcium intake, serum levels of free testosterone, bioavailable 17β-estradiol, PTH, 25-hydroxycholecalciferol, and creatinine. After adjustment for the confounders, men in the highest (fourth) quartile of OPG levels (>4.55 pmol/liter) had higher total cross-sectional area and trabecular area at the distal radius and distal tibia (3.3-6.0%, P < 0.05). At both skeletal sites, the highest OPG quartile was associated with lower cortical thickness (8.2%, P < 0.001, and 3.7%, P < 0.05) and volumetric bone mineral density (vBMD, 2.7%, P < 0.001, and 1.6%, P < 0.005) compared with the three lower quartiles combined. Associations of OPG level with trabecular vBMD, number, thickness, and distribution were not significant. Men in the fourth OPG quartile had higher levels of bone resorption markers (11.8-13.1%, P < 0.01-0.001). Men with higher serum OPG concentration had lower cortical thickness and vBMD, probably due to accelerated endo- and intracortical bone turnover, but higher cross-sectional area possibly due to periosteal apposition.