Figure 4.

The schematic diagram shows the effects of Lf in bone remodeling. The bone remodeling cycle comprises several stages, including quiescence, activation & resorption, reversal, and formation. In the activation & resorption stage, osteoclasts are recruited to the bone surface and resorb the old bone. In the reversal stage, osteoblasts are recruited to the bone surface to begin the process of new bone formation. The final stage involves the production of new bone matrix by osteoblasts, which undergoes mineralization. In the normal bone remodeling cycle, there is a balance between bone resorption and bone formation such that the amount of bone that is resorbed is replaced by an equal amount of new bone formation, resulting in the maintenance of a constant bone mass. In osteoporosis, there is an imbalance between bone resorption and formation because osteoclast activity is increased. In contrast, osteoblast activity is decreased, resulting in decreased bone mass and an increased risk of fractures. Lf acts at the activation & resorption phases by the mechanisms described in Figure 2 to inhibit bone resorption. Lf also acts at the reversal and formation stages to stimulate bone formation by the mechanisms described in Figure 1 . By these mechanisms, Lf corrects the remodeling cycle and restores bone mass. Osteioid, unmineralized bone matrix; osteon, mineralized bone matrix. Image is made using the Biorender Software.