Figure 2.

Graphical depiction of processes underpinning normal bone remodelling and osteoporosis (OP). The upper panel illustrates the classic phases occurring during normal bone remodelling, including migration of monocyte/macrophage precursors and differentiation towards osteoclasts precursors (pre-OCs) and mature multinucleated osteoclasts (OCs). Bone remodelling also requires a cross-talk between osteoblasts (OBs) and OCs to ensure a proper equilibrium between bone resorption and production. The lower panel describes the altered balance between bone resorption and formation in favour of bone resorption by OCs.