Linked from
The 14 pages that link to Erythropoiesis, each with the reason it gives.
IronRelated: Developing red blood cells require iron to make hemoglobin.
AnemiaRelated: Impaired red-cell production can reduce red blood cell mass.
ErythropoietinRelated: Erythropoietin's principal biological effect is to increase this process.
Hemolytic anemiaRelated: Whether marrow production can match destruction determines anemia severity.