A 68-year-old male comes to your office feeling weak and fatigued for the past 10 days. His past medical history is significant for stage III chronic kidney disease with a glomerular filtration rate (GFR) of 45 mL/min. Laboratory tests reveal a hemoglobin concentration of 8 g/dL. You diagnose the patient with anemia of chronic kidney disease. The principal mechanism in this disorder involves which of the following?