EPO and polycythemia: In a case report of an adolescent patient with polycythemia and a high burden of functional paragangliomas, belzutifan led to a marked reduction in paraganglioma biochemical secretion (norepinephrine, chromogranin A) and radiographic regression of paraganglioma tumors, a cessation of anti-hypertensive agents, and a reduction in EPO and hemoglobin levels, obviating the need for therapeutic phlebotomy [53].