FGF23 and nutritional disorder: It stimulates red blood cell production and reduces hepcidin to release iron from stores.(12) It has been reported that EPO affects both production and cleavage of FGF23.(13) In human studies with administration of recombinant EPO, iFGF23 remains normal or increases only slightly, while the increase in cFGF23 is more pronounced.(13) HIF1α is stabilized in the setting of hypoxia or iron deficiency and activates the production of EPO.