Lactate Dehydrogenase

What Is It, Function, Treatment, and More

Author:Georgina Tiarks

Editors:Alyssa Haag,Ian Mannarino, MD, MBA,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:David G. Walker

What is lactate dehydrogenase?

Lactate dehydrogenase (LDH), also known as lactic acid dehydrogenase, is an oxidoreductase enzyme that can transfer electrons. During glycolysis, glucose is transformed into pyruvate, which is metabolized to produce adenosine triphosphate (ATP) in the citric acid cycle and via oxidative phosphorylation. When oxygen is absent or limited, LDH catalyzes the conversion of pyruvate to lactate through a reversible reaction known as the anaerobic pathway. 

LDH is present in nearly all tissues in the body with skeletal muscle cells responsible for around 40% of the total lactate production. Since LDH is present in most tissues, the measurement of LDH in the blood can signify tissue turnover and is a non-specific way of determining tissue injury within the body.

LDH catalyzing pyruvate molecule into lactate.

What is the function of lactate dehydrogenase?

Lactate dehydrogenase is an enzyme used in the conversion of pyruvate, a product of glycolysis, to lactate and vice versa through a reversible reaction. Glycolysis is the pathway whereby glucose is converted into pyruvate for energy. When oxygen is present (i.e., aerobic), pyruvate is processed in the citric acid cycle (i.e., the Krebs cycle) and via oxidative phosphorylation to produce energy molecules in the form of ATP.

When oxygen is not present, oxidative phosphorylation is interrupted and lactate is produced through the anaerobic pathway as a way of recycling glucose for energy. In the forward reaction, NADH is changed to NAD+ through the removal of a hydrogen ion. Those hydrogen ions are then utilized for energy production. Once lactate is produced, it enters the bloodstream and is transported to the liver to be recycled in the Cori cycle (i.e., lactic acid cycle). 

The liver uses the reversible LDH enzyme to convert lactate back into pyruvate while also converting NAD+ to NADH through the addition of a hydrogen ion. Once pyruvate is created, it can be metabolized to glucose again in the liver. Glucose is then transported elsewhere in the body, such as to the muscles, to be broken down for energy. The net ATP produced during anaerobic metabolism is only two ATP compared to 36 ATP generated during aerobic metabolism.

Since LDH exists in the cytoplasm of most cells in the body, measuring lactate dehydrogenase can be a useful non-specific marker to suggest tissue damage. It can also be used as an indicator of further underlying disease.

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How do you measure lactate dehydrogenase?

Lactate dehydrogenase can be measured from blood or fluid from the body. The lactate dehydrogenase (LDH) test measures the amount of LDH that has leaked out from cells in the body when damaged. A healthcare professional can draw blood using a small needle that is inserted into a vein and analyze it using the LDH blood test. LDH can also be measured from other body fluids, including cerebrospinal fluid, pleural effusion fluid, and abdominal fluid. LDH is measured in units per liter, and for adults, a normal LDH range is typically 122 to 222 units per liter, depending on the laboratory and assay used.

What does it mean if lactate dehydrogenase is elevated?

Elevated lactate dehydrogenase can be caused by many underlying conditions, typically in conditions where there is not enough oxygen available or when there is tissue damage, causing release of LDH into the bloodstream. Typically, elevated LDH is considered when levels are greater than 222 units per liter. 

What causes elevated lactate dehydrogenase?

Most commonly, exercise or strenuous activity can cause elevated LDH levels. During exercise, muscles may not receive enough oxygen to accommodate for the energy that they require, and muscle cells will often turn to anaerobic metabolism for energy. Elevated LDH can also indicate that there is ongoing tissue damage from more serious underlying conditions. For instance, cancer cells require increased levels of energy production for their constant replication and often switch from oxidative phosphorylation to anaerobic metabolism, which is known as the Warburg effect. 

LDH can also be elevated in conditions affecting the respiratory system (e.g. pulmonary embolism), hematologic system (e.g. lymphoma, leukemia, anemia), cardiac system (e.g., heart attack), trauma, gastrointestinal system disease (e.g., pancreatitis, liver disease such as hepatitis and cirrhosis), kidney disease, or infectious disease (e.g. malaria, encephalitis, meningitis, HIV). The levels of LDH change with the severity of disease, so healthcare providers may use it as a non-specific marker for prognosis or to determine if treatment is working.

LDH can also be falsely elevated due to certain medications (e.g., narcotics, procainamide, aspirin) and alcohol

How is elevated lactate dehydrogenase treated?

Elevated lactate dehydrogenase can be treated by addressing the underlying cause. If LDH levels are high, a healthcare provider may want to order additional testing, which may include a complete blood count (CBC), complete metabolic panel (CMP), or other blood tests. An LDH isoenzyme test can also determine the specific types of LDH that are elevated, which can help to narrow down the origin. In certain situations, the healthcare provider may recommend treatment with ascorbic acid (i.e., vitamin C), which may lower LDH levels.

What are the most important facts to know about lactate dehydrogenase?

Lactate dehydrogenase (LDH) is an oxidoreductase enzyme that catalyzes the reversible conversion of pyruvate to lactate. When adequate oxygen is available (i.e., aerobic), pyruvate continues to the Krebs cycle and oxidative phosphorylation to produce energy in the form of ATP. However, during times of inadequate oxygen, the anaerobic pathway is used, which increases the production of LDH. The LDH test measures the amount of LDH in the blood or bodily fluids, which is a useful, though non-specific, marker of tissue damage. LDH can be elevated due to a multitude of causes, such as strenuous exercise, cancer, anemia, liver disease, kidney disease, cardiovascular disease, among others. Treatment depends on the underlying cause.

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Resources for research and reference

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