In contrast to wild-type and VDRΔ/Δ mutant mice, rFGF23 treatment of 3-month-old Kl−/−/VDRΔ/Δ double mutant mice did not result in renal Na+ retention and heart hypertrophy (Fig 4B), showing that the effects of FGF23 on Na+ homeostasis and heart hypertrophy are Klotho dependent, but VDR independent. The gene discussed is FGF23; the disease is cardiac hypertrophy.