LDH is an enzyme that catalyzes the interconversion of lactate and pyruvate in the presence of NAD/NADH. It is widely distributed in body cells and fluids and since its RBC/plasma ratio is high, it is spuriously elevated in plasma/serum following hemolysis.
Normal Range: Laboratory-specific
increased in: Tissue necrosis, especially in acute injury of cardiac muscle, RBCs, kidney, skeletal muscle, liver, lung, skin. Commonly elevated in various carcinomas and in Pneumocystis carinii and B cell lymphoma in AIDS. Marked elevations occur in hemolytic anemias, vitamin B12 deficiency anemia, folate deficiency anemia, polycythemia vera, acute (but not chronic) hepatitis, cirrhosis, obstructive jaundice, renal disease, musculoskeletal disease, CHF. Drugs causing hepatotoxicity or hemolysis.
Decreased in: Clofibrate,
fluoride (low dose).
Additional: LDH
is elevated after myocardial infarction (2-7 days), in liver congestion
(eg, in CHF) and in Pneumocystis carinii pneumonitis. LDH is not a useful
liver function test and it is not specific enough for the diagnosis of
hemolytic or megaloblastic anemias. Its main diagnostic use is in myocardial
infarction in which the CKMB elevation has passed. With the availability
of specific LD1 measurements, the total LD level may no longer be useful.
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