Erythropoietin, often called EPO, is a hormone primarily produced by the kidneys. Its main function is to stimulate the bone marrow to produce red blood cells, which are responsible for carrying oxygen throughout the body. When levels of EPO are elevated, it can signal an underlying health condition that requires further investigation.
Understanding Erythropoietin
The kidneys are the primary site of erythropoietin production, with specialized cells in the renal cortex detecting blood oxygen levels. When oxygen levels in the blood drop, a condition known as hypoxia, the kidneys increase their output of EPO. This hormone then travels to the bone marrow, prompting it to accelerate the production of new red blood cells.
This process is a feedback loop designed to maintain the body’s oxygen-carrying capacity. As more red blood cells are produced, oxygen delivery to tissues improves, and the kidneys respond by reducing EPO production. Normal EPO levels range between 4 and 26 mU/mL.
Reasons for Elevated Erythropoietin
Elevated erythropoietin levels are a response to the body’s need for more oxygen. One common cause is a physiological response to chronic low oxygen levels, known as hypoxia. This can occur in individuals living at high altitudes, or in those with chronic lung diseases such as chronic obstructive pulmonary disease (COPD) or emphysema, which impair lung function and oxygen uptake. Severe anemia also triggers increased EPO production. Conditions affecting the heart that hinder efficient oxygen circulation, or even sleep apnea, can also lead to sustained low oxygen.
Beyond the body’s natural response to hypoxia, certain kidney-related conditions can also cause elevated EPO. While kidney disease often leads to decreased EPO production, some specific kidney issues can have the opposite effect. These include conditions like kidney cysts, renal artery stenosis, and polycystic kidney disease, all of which can lead to localized hypoxia within the kidney tissue, prompting increased EPO release. Certain tumors can produce EPO independently of the body’s oxygen needs. These EPO-secreting tumors can originate in various organs, such as renal cell carcinoma, liver tumors, or cerebellar hemangioblastomas. Additionally, some less common causes for elevated EPO include certain blood disorders or the administration of exogenous EPO, such as in cases of performance enhancement.
Associated Health Concerns
Chronically elevated erythropoietin levels can lead to an overproduction of red blood cells, known as polycythemia or erythrocytosis. This increase in red blood cell count makes the blood thicker. Increased blood viscosity can impede blood flow, leading to a higher risk of serious cardiovascular complications.
These complications include the formation of blood clots, which can obstruct blood vessels and lead to events such as strokes or heart attacks. Individuals with polycythemia may experience various symptoms as a result of the thickened blood and impaired circulation. Symptoms include headaches, dizziness, and fatigue. Other symptoms can include blurred vision, itching, and joint pain.
Diagnosis and Treatment Approaches
Diagnosing elevated erythropoietin typically begins with blood tests that measure EPO levels and a complete blood count (CBC) to assess the red blood cell mass. A normal range for EPO levels is generally between 4 and 26 mU/mL, but results can vary between laboratories and should be interpreted by a healthcare provider. If elevated EPO is detected, further diagnostic tests are often necessary to pinpoint the underlying cause.
These additional tests may include imaging studies, such as ultrasounds or CT scans, to examine the kidneys or other organs for abnormalities, or a bone marrow biopsy to assess the bone marrow’s red blood cell production. Treatment for elevated EPO focuses primarily on addressing the root cause. This could involve managing chronic lung diseases to improve oxygenation, treating kidney conditions, or, in cases of EPO-producing tumors, surgical removal. If polycythemia is present and causing symptoms or significant risk, management might include phlebotomy, a procedure to remove excess red blood cells from the bloodstream, to reduce blood viscosity.