Osteoprotegerin (OPG), a decoy receptor for RANKL, protects bone from excessive resorption by competitively binding to RANKL, thereby inhibiting the RANKL/RANK signaling pathway.140 Given its critical function in regulating bone metabolism, the RANKL/RANK/OPG axis is indispensable for maintaining bone homeostasis, and dysregulation of this system can contribute to bone-related disorders, including osteoporosis. The gene discussed is TNFSF11; the disease is osteoporosis.