Lactate dehydrogenase (LDH) – how does the enzyme work? When to do the LDH test?

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Lactate dehydrogenase (LDH) is a cytoplasmic enzyme present in all cells. It occurs in 5 isoenzymes: LDH1-2 – mainly in the heart muscle as well as red blood cells and the kidney cortex, LDH3 – in the lungs and cancer cells, LDH4-5 – in skeletal muscles and the liver.

Lactate dehydrogenase (LDH) – what is it?

Lactate dehydrogenase (LDH) is an enzyme that is found in the cells of the human body and is involved in the conversion of glucose. It penetrates into the blood serum without major complications as a result of cell death, blood ion imbalance or increased cell membrane permeability. Its increased level results from the release of LDH outside at the time of cell damage. Lactate dehydrogenase testing performed in conjunction with other tests, eg CRK, GOT, allows the physician to make decisions in the event of tissue damage or abnormalities in membrane permeability. In addition, LDH testing is associated with liver disease and the differentiation of jaundice. The level of dehydrogenase provides very important a prognostic element in genital cancers, leukemias and lymphomas. In patients with myocardial infarction, the serum level of LDH rises within 12 hours, and its maximum concentration is reached after 48-72 hours.

There are several types of lactate dehydrogenase (LDH), depending on where it occurs:

  1. LDH1 and 2 (heart)
  2. LDH3 (lungs)
  3. LDH4 (kidneys, pancreas, placenta)
  4. LDH5 (liver, skeletal muscle)

When do we do the lactate dehydrogenase (LDH) test?

LDH testing should be performed in the following cases:

1. Suspicion of proliferative diseases of the hematopoietic system (leukemia).

2. Suspicion of haemolytic anemia.

3. Suspected damage to the heart muscle cells (heart attack, inflammation, failure).

4. Diseases of the biliary tract (damage to hepatocytes as a result of inflammation, toxins or tumors).

5. Damage to skeletal muscles (myopathies).

6. Suspicion of neoplastic disease.

7. Suspicion of lung diseases (lung infarction, lung cancer).

LDH is also useful in the diagnosis of acute pancreatitis. LDH determination is also performed in people with HIV, in which case lactate dehydrogenase is considered a marker of pneumonia caused by Pneumocystis jiroveci. High levels of LDH in people with HIV may also indicate mycosis or histoplasmosis.

Lactate dehydrogenase (LDH) study

Material for LDH testing: serum.

Preparation for the test: on an empty stomach (at least 8 hours).

The course of the LDH test: one-time blood sampling from a vein in the arm.

Time to wait for the result: 1 Day.

Standard: 20-80 nmol/l/s; izoenzym LDH1 makes up about 50% of LDH4 – about 30%, and LDH5 – about 35% of total LDH activity.

Comments: Under normal conditions, low levels of LDH are found in the serum. This enzyme enters the serum in greater amounts in the event of cell damage (necrosis) or in the case of an increase in the permeability of cell membranes due to ischemia, changes in ion concentrations or the action of toxins, or in rapidly growing (cancerous) cells. Increasing the concentration of LDH in the serum confirms cell damage, although it does not determine its location unequivocally.

Lactate dehydrogenase (LDH) – test analysis and norm

What is a good LDH test result?

  1. adults: less than 480 IU / l,
  2. genital cancer marker – less than 270 IU / l.

The level of lactate dehydrogenase is significantly related to the stage of the disease:

  1. a level above 600 IU / l is a bad prognosis in the case of severe pancreatitis (acute or viral),
  2. very high activity of lactate dehydrogenase appears 12 hours after a heart attack and lasts up to 10 days,
  3. in the case of Hodgkin’s disease, high levels of lactate dehydrogenase (LDH) suggest advanced disease,
  4. high LDH in neoplastic disease indicates disease relapse,
  5. if you have jaundice and your LDH / AST ratio (AST is one of the liver enzymes) is above 5, you may suspect jaundice from breakdown of red blood cells.

The following may also contribute to the increase in lactate dehydrogenase levels:

  1. muscle atrophy,
  2. stroke,
  3. anemia
  4. kidney disease
  5. liver disease (e.g. liver cancer)
  6. taking medications, e.g. aspirin, narcotic preparations,
  7. taking alcohol,
  8. melanoma,
  9. testicular cancer,
  10. lymphoma,
  11. infectious mononucleosis,
  12. haemolytic or megaloblastic anemia,
  13. pulmonary embolism.

High concentration of this enzyme is also observed in pregnant women, as well as newborns and people after intense physical exertion. Please note that the reference standards may differ depending on the laboratory where the assay was performed.

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