Which statement best describes the RANKL/OPG axis in periodontal bone loss?

Which statement best describes the RANKL/OPG axis in periodontal bone loss?

• A. OPG stimulates osteoclast formation.
• B. RANKL stimulates osteoclast formation leading to bone resorption; OPG is a decoy receptor; dysregulation promotes periodontitis-related bone loss.
• C. RANKL inhibits osteoclast formation.
• D. OPG is a cytokine that directly kills osteoclasts.

Answer: (B)

Key concept: the balance between RANKL and OPG controls osteoclast formation and bone resorption. RANKL binds to its receptor RANK on osteoclast precursors, triggering their differentiation and activity so bone is resorbed. OPG acts as a decoy receptor, binding RANKL and preventing it from activating RANK, thereby dampening osteoclast formation. In periodontal disease, inflammatory signals raise RANKL levels and often lower OPG, tipping the balance toward bone loss around teeth. That makes the statement describing RANKL as a stimulator of osteoclast formation and OPG as a decoy receptor, with dysregulation promoting periodontitis-related bone loss, the best description. The other options misassign either the role of RANKL or OPG (RANKL does not inhibit osteoclasts; OPG is not a cytokine that kills osteoclasts).