Overview
Lactate dehydrogenase is an important intracellular enzyme involved in anaerobic metabolism and belongs to the oxidoreductase class of enzymes. It catalyzes the reversible conversion of pyruvate to lactate with simultaneous interconversion of NAD⁺ and NADH, playing a crucial role in cellular energy generation, especially under anaerobic conditions. Lactate dehydrogenase is widely distributed in almost all body tissues, with higher concentrations found in muscle, liver, kidney, heart, brain, and red blood cells. When tissue injury or disease occurs, Lactate dehydrogenase is released into the bloodstream or body fluids, making it a useful biochemical marker of tissue damage. Although LDH isoenzyme patterns were historically used in myocardial infarction diagnosis, this role has largely been replaced by cardiac troponins.
Symptoms
Lactate dehydrogenase elevation itself does not cause symptoms. Clinical manifestations depend on the underlying condition causing tissue damage. Patients may present with symptoms related to myocardial infarction, liver disease, hemolytic anemia, muscle injury, infections, malignancy, or neurological disorders. LDH serves as a laboratory indicator reflecting the extent and severity of cellular injury rather than a symptom-producing factor.
Causes
LDH levels rise when there is damage to tissues or increased cellular turnover. Causes include myocardial infarction, liver injury, hemolysis, muscle trauma, infections, inflammatory conditions, malignancies, renal failure, and neurological insults such as stroke or encephalitis. LDH is directly proportional to the nature and severity of tissue injury, and persistent elevation often reflects ongoing damage or disease progression. In oncology, elevated LDH levels result from tumor-related tissue destruction and increased metabolic activity.
Risk Factors
Conditions associated with raised LDH levels span multiple organ systems. Hematological disorders such as leukemia, lymphoma, hemolytic anemia, and sickle cell disease commonly elevate LDH. Hepatic diseases, including hepatitis, cirrhosis, and liver metastases, contribute to increased levels. Musculoskeletal conditions such as muscular dystrophy, inflammatory myositis, strenuous exercise, and trauma are additional risk factors. Neurological conditions like stroke, meningitis, and encephalitis, as well as systemic infections, sepsis, burns, autoimmune disorders, and malignancies, are also strongly associated. Genetic deficiencies of LDH subunits due to mutations in LDHA or LDHB genes, inherited in an autosomal recessive pattern, can affect carbohydrate metabolism in muscle cells.
Prevention
There are no specific preventive measures to directly control LDH levels, as LDH reflects underlying disease processes. Prevention focuses on early diagnosis and management of the causative condition. Accurate interpretation requires proper sample collection, including the use of serum from non-hemolysed blood samples, as hemolysis can falsely elevate LDH levels. LDH measurement is valuable for monitoring disease progression and response to therapy, particularly in oncology, where declining levels indicate treatment response and persistently elevated levels suggest poor prognosis or treatment failure. Despite its broad clinical utility, LDH lacks specificity and sensitivity and should always be interpreted alongside clinical findings and other laboratory parameters.
