Clinical Significance

    LDH is an enzyme found in the cells of many body tissues, including the heart, liver, kidneys, skeletal muscles, brain, RBC's, and lungs. It is responsible for converting muscle lactate into pyruvate, an essential step in producing cellular energy. It is composed of four peptide chains of 2 subunits (M form and H form) which results in up to 5 different isoenzymes which can be separated and quantitated by electrophoresis. Measurement of the total LDH activity in serum or plasma is non-specific and cannot differentiate the tissues of origin of the component isoenzymes.

LDH is used in the differential diagnosis of hemolytic anemia and as a tumor marker in some malignancies such as germ cell tumors.

LDH is elevated in hepatitis, glomerular nephritis, pulmonary embolism, muscle disease and many leukemias and lymphomas.

As LDH is a non-specific marker, it is used in combination with other markers in diagnosis and patient management.