Effects of PEG-rHuMGDF on hematopoiesis in untreated controls. PEG-rHuMGDF (2.5 μg/kg/d) increased the concentration of circulating platelets sixfold by 2 weeks. The platelet count normalized within 10 days after stopping therapy (left). Peripheral leukocyte, neutrophil, or erythrocyte counts did not change significantly during PEG-rHuMGDF administration (right).