However, we actually found a decreased heart/body weight ratio in 4-week-old Kl−/− mice, and unchanged heart/body weight ratio in Kl−/−/VDRΔ/Δ mice compared to wild-type and VDRΔ/Δ littermates (Supplementary Fig S6), suggesting that chronically elevated endogenous Fgf23 serum levels in Kl−/− mice do not cause heart hypertrophy in the absence of the co-receptor Klotho. Here, FGF23 is linked to cardiac hypertrophy.