Certain kidney tumors that produce EPO would likely have what effect on erythrocyte production?

• A. Decreased erythrocyte production
• B. No effect on erythrocyte production
• C. Constant stimulation of erythrocyte production
• D. Variable stimulation depending on tumor size

Answer: (C)

When kidney tumors produce excess erythropoietin (EPO), they lead to an increase in erythrocyte production. EPO is a hormone primarily produced by the kidneys in response to low oxygen levels in the blood; its primary function is to stimulate the bone marrow to produce more red blood cells (erythrocytes).

In this case, tumors that secrete EPO would continuously stimulate the erythropoiesis process, potentially leading to an elevated red blood cell count known as polycythemia. This constant stimulation occurs because the tumor cells may produce EPO regardless of the body's actual oxygen levels, bypassing the normal regulatory mechanisms that control erythrocyte production.

Therefore, the presence of these kidney tumors would lead to a sustained increase in erythrocyte production, resulting in the correct answer being that there is constant stimulation of erythrocyte production.