Erythropoietin
Overview
Erythropoietin (EPO) is a glycoprotein hormone primarily produced by peritubular fibroblasts in the kidney that stimulates red blood cell production (erythropoiesis) in bone marrow by binding to EPO receptors on erythroid progenitor cells. It responds to hypoxia via hypoxia-inducible factor (HIF) pathway activation. Elevated levels occur in hypoxia, high-altitude exposure, inappropriate EPO secretion (tumors, renal cysts), or polycythemia vera workup, while low levels indicate chronic kidney disease, anemia of chronic disease, or iron deficiency. Clinically, EPO measurement helps differentiate causes of polycythemia and guides therapy in renal failure-related anemia.
Clinical Use Cases
- Differentiating primary polycythemia vera from secondary polycythemia.
- Evaluating polycythemia in smokers, high-altitude residents, or renal disease.
- Assessing inappropriate EPO production by tumors (renal cell carcinoma, hepatocellular carcinoma).
- Monitoring response to recombinant EPO therapy in chronic kidney disease.
Specimen Types
- Serum.
- Plasma (EDTA or heparin).
Measurement Methods
- Two-site chemiluminescent immunometric assay.
- Enzyme-linked immunosorbent assay (ELISA).
- Radioimmunoassay (less common).
Test Preparation and Influencing Factors
- No fasting required.
- Recent blood loss, hemolysis, or transfusion lowers EPO.
- Smoking, high altitude, or acute hypoxia transiently elevate levels.
- Recombinant EPO therapy interferes with immunoassays.
Synonyms
- EPO.
- Erythropoetin.
- Hematopoietic growth factor.