This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
The primary cause of anemia in chronic kidney disease (CKD) is: 
Select and explain. 
A. Chronic inflammation, B. Iron deficiency, C. Erythropoetin deficiency, D. Diminished red blood survival
C: Erythropoetin deficiency
Answer: C: Erythropoetin deficiency 
Explanation: All are causes of anemia in CKD, the primary cause is insufficient production of erythropoetin by the diseased kidneys. Other causes are; Bleeding diathesis Hyperparathyroidism/bone marrow fibrosis Folate or vitamin B12 deficiency Hemoglobinopathy Ref: Harrisons principles of internal medicine, 18th edition, Page: 2316.