While the analysis of cardiac function in FGF21-Tg mice was confounded by their significantly reduced body weight and apparent failure-to-thrive, by echocardiography these mice exhibited a persistent elevation in ejection fraction and relative LV hypertrophy, as indicated by increased LV mass to body weight ratio and relative wall thickness (“concentricity index”)40, consistent with the development of concentric cardiac hypertrophy (Fig. 1d–f; Supplementary Fig. 1a; Supplementary Table 1). Here, FGF21 is linked to Failure to thrive.