An enzyme found in all tissues, especially the liver and muscle tissue. Five different isoforms are known from LDH1 (cardiac muscle and brain tissue) to LDH5 (liver, muscle tissue and saliva). Serum LDH begins to increase 12 to 24 hours after myocardial infarction, reaches a peak level on the second or third day and returns to normal within about ten days, therefore measuring its level is useful in this condition, especially well after the event. This test is also useful in the diagnosis of pulmonary embolism in which LDH levels rise without any parallel increase in total creatine kinase. LDH may also increase following electric shock and in prolonged tachycardia, hemolytic anemia, hepatocellular damage and hepatic metastasis. See Lactate Dehydrogenase (LDH) Isoenzymes, Serum
Total serum LDH is measured. For alternative sample type, call the chemistry department. Allow serum tube to clot completely at room temperature.