Regulation of FGF23 and its autocrine/paracrine effects on osteoclast and bone resorption. A decrease in osteoclastogenesis by downregulating RANKL expression may be mediated by FGF23 via an unknown mechanism. The biphasic physiological effects of FGF23 via FGFR on human monocyte-derived osteoclast cultures inhibit the early stages of osteoclastogenesis from osteoclast progenitors but substantially inhibited osteoclast-mediated bone resorption. However, the hypothesis that FGF23 may influence RANKL expression, osteoclastogenesis, and osteoclast-mediated bone resorption requires further confirmation. The symbol “?” and dash lines denote issues of controversy and unknown mechanism, respectively. This figure was generated with publication licensed by BioRender, Toronto, ON, Canada (Agreement number: NS237SOEQK, 19 November 2021). Abbreviations: FGF23, Fibroblast growth factor 23; RANK, Receptor activator of nuclear factor-κΒ; RANKL, Receptor activator of nuclear factor-κΒ ligand.