EPO and Renal artery stenosis: Acquired• Hypoxia-driven (chronic lung disease, right-to-left cardiopulmonary shunts, high-altitude habitat, tobacco use, carbon monoxide poisoning, sleep apnea syndrome, and renal artery stenosis)• Hypoxia-independent   ° Pathologic EPO production (e.g., EPO-producing tumors)   ° Exogenous EPO administration (drug related)