In patients with renal cell carcinoma, which paraneoplastic syndrome is often associated with elevated levels of erythropoietin (EPO)?

In renal cell carcinoma, the tumor can produce ectopic erythropoietin (EPO), leading to secondary polycythemia. This is a paraneoplastic syndrome where elevated levels of EPO stimulate the bone marrow to increase the production of red blood cells, resulting in an increased hemoglobin concentration and hematocrit. This phenomenon occurs because renal cell carcinoma has the capacity to secrete various substances, including hormones like EPO, which is normally produced by the kidneys in response to low oxygen levels.

Secondary polycythemia is particularly significant because it can manifest as symptoms related to hyperviscosity, such as headaches, dizziness, and an increased risk of thrombosis. Thus, the association of renal cell carcinoma with elevated erythropoietin levels, resulting in secondary polycythemia, highlights the complex interplay between tumors and systemic metabolic responses in the body.

In the context of the other options, while hypercalcemia, Cushing's syndrome, and hypoglycemia can occur in various neoplasms, they are not typically associated with renal cell carcinoma in the way that secondary polycythemia is. Hypercalcemia often occurs in association with malignancies that metastasize to bone or those that produce parathy