FGF23 and Iron deficiency anemia: Under healthy conditions increased transcription due to iron deficiency and/or inflammation are matched with increased cleavage to maintain normal circulating levels of full-length FGF23, resulting in elevated concentrations of circulating cFGF23, but normal concentrations of iFGF23 and hence a better correlation of cFGF23 with outcomes as compared with iFGF23 measurements.