FGFR4 and cardiac hypertrophy: Since we previously found that FGF23/FGFR4 signaling in cardiac myocytes induces cardiac hypertrophy by activating calcineurin/NFAT signaling [23,34], which has been shown to act as an inducer of pregnancy-associated cardiac hypertrophy [35], we aimed to determine whether FGFR4 is required for the development of physiologic cardiac hypertrophy in pregnant mice and to identify the source of FGF23 in pregnancy.