Reduced Bone Modeling and Unbalanced Bone Remodeling: Targets for Antiresorptive and Anabolic Therapy

Abstract

Bone loss during advancing age is the net result of reduced modeling-based bone formation upon the outer (periosteal) envelope and unbalanced remodeling by basic multicellular units (BMUs) upon the three (intracortical, endocortical, and trabecular) components of the inner (endosteal) bone envelope. Each BMU deposits less bone than resorbed, reducing total bone volume and deteriorating the microstructure of the diminished residual bone volume. Antiresorptive agents like bisphosphonates reduce, but do not abolish, the rate of bone remodeling – fewer BMUs remodel, “turn over,” the volume of bone. Residual unbalanced remodeling continues to slowly reduce total bone volume and deteriorate bone m..