Lactate dehydrogenase (LDH) is a common enzyme found within nearly all cells of the body. Its levels are sometimes measured in the blood to provide insights into various health conditions. This measurement can indicate general tissue damage or cellular injury. Understanding LDH levels helps healthcare providers assess overall health and guide further diagnostic steps.
What is Lactate Dehydrogenase (LDH)?
Lactate dehydrogenase (LDH) is an enzyme that plays a role in cellular energy production, converting glucose into energy for cells. It is involved in the anaerobic metabolic pathway, converting lactate to pyruvate and regenerating NAD+. This enzyme is found in almost all tissues throughout the body, with higher concentrations in organs such as the heart, liver, kidneys, muscles, brain, and blood cells. When cells are damaged or destroyed, LDH leaks from these tissues into the bloodstream, leading to elevated levels.
Defining High LDH Levels
A typical “normal” range for LDH levels in adults generally falls between 140 and 280 units per liter (U/L). However, these ranges can vary between different laboratories due to varying measurement systems and methodologies. Factors such as age also influence normal levels, with infants and young children typically having significantly higher normal LDH concentrations; for instance, newborns may have levels between 135 and 750 U/L.
An LDH level is considered “high” or “elevated” when it exceeds the upper limit of the established normal range for a particular laboratory and patient demographic. A result above these values would be considered elevated, but the numerical definition of “high” is always relative and requires medical interpretation in the context of a patient’s overall health and symptoms.
LDH as a Cancer Indicator
Elevated LDH levels can be associated with cancer, although it is not a specific diagnostic marker for the disease. Cancer cells often exhibit altered metabolism, favoring a process that produces more lactate, which LDH then converts. This metabolic shift results in increased LDH levels. Additionally, rapidly growing tumor cells can release LDH into the bloodstream when they die or are damaged.
Higher LDH levels can indicate increased tumor burden, higher cell turnover, or tumor lysis. While LDH cannot diagnose cancer on its own or identify a specific type, it serves as a general indicator of tissue damage or rapid cell turnover, which can be associated with malignancy. Its measurement is used in monitoring disease progression, assessing treatment response, and determining prognosis for certain cancers, including lymphoma, melanoma, germ cell tumors, and lung cancer. For instance, decreasing LDH levels during treatment can suggest a positive response to therapy, while increasing levels might indicate that the cancer is not responding well.
Non-Cancer Causes of High LDH
Elevated LDH levels are not exclusive to cancer and can result from various non-cancerous conditions. Common causes include:
Strenuous exercise, which can lead to muscle damage.
Tissue injuries, such as muscle trauma, rhabdomyolysis, or bone fractures.
Infections, including mononucleosis, pneumonia, or severe infections like malaria.
Inflammatory conditions.
Liver diseases like hepatitis or cirrhosis.
Kidney diseases.
Blood disorders, particularly hemolytic anemia, where red blood cells are prematurely destroyed.
Certain medications, surgical trauma, or burns.
What to Do After a High LDH Result
Receiving a high LDH test result warrants consultation with a healthcare professional for proper interpretation. Elevated LDH is a non-specific marker, meaning it can be high due to many different causes, both cancerous and non-cancerous. A healthcare provider will consider the LDH result in conjunction with your symptoms, medical history, and other diagnostic findings to determine the underlying reason for the elevation.
Further diagnostic tests are almost always necessary to pinpoint the cause of elevated LDH. These may include additional blood tests, imaging studies like X-rays or CT scans, or biopsies, depending on what the healthcare provider suspects. It is important to avoid self-diagnosis or panic, as LDH is only one piece of a larger diagnostic puzzle and is often elevated due to benign conditions.