EPO and diabetes mellitus: Non‐classical regulators of FGF23 include iron status, inflammation, erythropoietin, hypoxia‐inducible factor 1α (HIF1α), insulin and diabetes, and leptin.(7) The FGF23 gene encodes for a 251‐amino‐acid‐long glycoprotein that requires posttranslational O‐glycosylation in order to be stabilized and phosphorylation to be cleaved.(3, 7) Currently, two types of FGF23 assays exist for the quantification of circulating FGF23 concentrations in humans.