LDH 120 - 300 HIGH

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an elevated LACTATE DEHYDROGENASE (LDH) level greater than 300 IU/L. Lactate dehydrogenase is a hydrogen transfer enzyme that strongly favors and catalyzes reduction of pyruvate to lactate at physiologic pH. LDH activity is present in all cells of the body and is invariably found in the cytoplasm. Highest LDH concentrations can be found in liver, heart, kidney, skeletal muscle and red blood cells. If any of these tissues are damaged they release LDH. Concentrations of LDH are 500 times higher in these tissues; therefore, even a small amount of leakage can have a significant effect on serum LDH levels. There are five isoenzymes of LDH and these are generally tissue specific:

LDH1 - cardiac, kidney, RBCS

LDH2 - RBCS, kidney, cardiac

LDH3 - endocrine glands, spleen, lung, lymph nodes, platelets, and non-gravid uterine muscles

LDH4 - liver, skeletal muscle

LDH5 - skeletal muscle, liver

LDH levels can help determine acute or recent myocardial infarction (MI). Levels increase between 24 to 48 hours post MI and remain elevated for 7-14 days. Elevations are usually three to four times normal but can be as high as ten times normal. Moderately elevated levels are associated with myocarditis, congestive heart failure, and hepatic congestion. LDH is normal in angina and pericarditis. In myocardial infarction, the LDH1 /LDH2 ratio is greater than one. Normally, the LDH1 is less than the LDH2 and increases after myocardial muscle injury, hemolytic anemia, vitamin B12 deficiency anemia, folate deficiency anemia, and testicular carcinoma. LDH3 is elevated with acute pulmonary infarction and pneumonia. LDH5 is elevated in liver disease, and when LDH5 is greater than LDH4, this is indicative of hepatic pathology. LDH is used as a marker to infer the diagnosis of PCP in persons afflicted with HIV who present with symptoms of pneumonia, a CD4 count of 200 or less, diffuse interstitial infiltrates on chest radiograph and characteristic ABG changes (hypoxia and an elevated A-a gradient). LDH is also a nonspecific tumor marker, and its unexplained elevation in the proper setting should initiate a malignancy workup.