GDF15 and heart failure: At enrollment, 12 of 55 patients were in NYHA functional class III or IV heart failure and showed a significantly higher GDF-15 levels (2032.0 ± 1108.0 vs 1305.0 ± 619.0 ng/l, P = 0.002) as compared to those patients in NYHA functional class I and II (Fig. 2C).