FGF23 and chronic kidney disease: Although we found no differences in Fgf23 mRNA levels in liver, another source of FGF23 (Agoro et al., 2021; White et al., 2000), potentially marrow (Clinkenbeard et al., 2017) or spleen (Bansal et al., 2017) could secrete enough FGF23 during CKD to attempt to maintain serum levels.