High Quality Content by WIKIPEDIA articles! Osteoprotegerin (OPG), also known as osteoclastogenesis inhibitory factor (OCIF), or tumor necrosis factor receptor superfamily member 11B (TNFRSF11B), is a protein that in humans is encoded by the TNFRSF11B gene. Osteoprotegerin is a cytokine receptor, and a member of the tumor necrosis factor (TNF) receptor superfamily.