FGF23 and chronic kidney disease: Since the levels of FGF23 in the Dmp1 null mouse have been measured between ~900 and 1400 pg/ml at 5–6 months of age (Feng et al., 2006; Liu et al., 2008; Lu et al., 2011), it is possible that these hearts did not develop pathological hypertrophy because FGF23 did not reach high enough serum levels or that FGF23 at lower serum levels works in concert with other factors (such as those present in chronic kidney disease–CKD) to induce pathological hypertrophy.