Erythropoetin

Erythropoietin (EPO) is a glycoprotein hormone primarily responsible for the regulation of red blood cell production (erythropoiesis) in mammals. It is synthesized mainly by specialized fibroblast-like cells in the renal cortex, with a smaller contribution from hepatic cells, especially during fetal development. Circulating EPO binds to erythropoietin receptors on erythroid progenitor cells in the bone marrow, stimulating their proliferation, differentiation, and survival, thereby increasing the number of circulating erythrocytes. Its secretion is up‑regulated in response to hypoxia, anemia, or reduced oxygen delivery, mediated by hypoxia‑inducible factor (HIF) pathways.

Recombinant human erythropoietin (rHuEPO) was first approved for clinical use in the late 1980s and is employed to treat anemia associated with chronic kidney disease, chemotherapy, or HIV infection. In addition, EPO analogs and longer‑acting formulations have been developed to reduce dosing frequency. While effective in correcting anemia, exogenous EPO can increase the risk of hypertension, thromboembolic events, and, in some cases, tumor progression, prompting careful monitoring of hemoglobin targets and dosing.

Erythropoietin has also been investigated for neuroprotective and tissue‑repair properties, but these applications remain experimental. Measurement of serum EPO levels can aid in diagnosing disorders of erythropoiesis, such as polycythemia vera (low EPO) or secondary erythrocytosis (elevated EPO). The hormone’s regulation, therapeutic use, and potential adverse effects continue to be subjects of active research within hematology and nephrology.