HAMP and acquired polycythemia vera: Patients with PV exhibited increased hematocrit and red cell count, and reduced ferritin (log ferritin: PV, 1.211 vs control, 1.572; P = .0002) and transferrin saturation (PV, 12.1% vs control, 24.43%; P < .0001); hepcidin levels were reduced (PV, 6.89 ng/mL vs control, 17.01 ng/mL; P < .0001), and erythroferrone levels increased (PV, 12.41 ng/mL vs control, 4.26 ng/mL; P = .0004).