Osteoprotegerin (OPG) or Osteoclastogenesis inhibitory factor (OCIF) is a dimeric glycoprotein of the TNF receptor family. OPG is produced in many different tissues such as bone and liver. OPG inhibits the binding of RANK to RANKL inhibiting formation and activation of osteoclasts. Changes of the OPG/RANKL ratio may be the major cause of bone loss in many bone metabolism diseases such as osteoporosis and osteopetrosis. Sample types: Mouse, Rat Cell Culture, Plasma, Serum, Urine. Range: 125 - 4000 pg/mL, Sensitivity: 125 pg/mL