GDF15, EPO, and sTfR levels in healthy controls and congenital dyserythropoietic anemia (CDA) I patients. Serum concentrations of (A) GDF15, (B) EPO, and (C) sTfR from healthy volunteers (HV) and patients with CDA I. Mean values (bars) and levels for individual volunteers (○) are shown. *P < .05.