TNFSF11 and osteoporosis: Central amongst these are RANKL (encoded by the TNFSF11 gene), the major osteocyte-derived osteoclastogenic cytokine3, 4 and an FDA-approved osteoporosis drug target, and sclerostin (encoded by the SOST gene), an osteocyte-derived WNT pathway inhibitor that blocks bone formation by osteoblasts5 and current osteoporosis drug target6.