LDH designates a class of enzymes, Lactase dehydrogenases. They are found everywhere in the body, whether in the muscles (and even the heart), in the tissues of the lungs or in the blood cells. An enzyme is a protein whose role is to catalyze reactions within the body, in other words to trigger them or speed up a process that is usually very slow.

There are several types, or isoenzymes, noted by number according to their location. Thus those of the heart or brain receive the status of LDH 1 and 2, while those of the platelets and lymph nodes are LDH3, those of the liver LDH 4 and those of the skin LDH5.

The role of LDH within the body is to catalyze the transformation of pyruvate into lactate, and vice versa. These two acids have a role of energy transfer between cells.

Note that it is also called lactate dehydrogenase, or lactic dehydrogenase, and is sometimes symbolized by LD.

The medical interest of LDH enzymes is above all to detect the abnormal increase in their presence. Normally, LDH is retained within the body’s cells. But if tissues are damaged, they will spill, and therefore catalyze more and more pyruvate into lactate.

Identifying them in specific areas or monitoring their behavior in the body can thus make it possible to determine an area that has suffered cell damage, or to assess its severity. It is also useful for spotting a range of ailments, ranging from anemia to cancer (see “Interpretation of the LDH result”).

The examination of the LDH dosage is carried out by simple blood sampling. More specifically, the laboratories will analyze the serum, the liquid in which blood constituents such as red blood cells bathe. Although the latter also have LDH enzymes in their hearts, it is above all the dose of the serum that counts in determining whether the level is abnormal or not.

The reference value for the assay of the LDH enzyme is evaluated at 120 to 246 U / L (units per liter).

To follow up the examination, the medical practitioner can analyze the results provided by the laboratory, and possibly identify various disorders in the patient. Often, it will be necessary to associate this result with the level of other enzymes or acids, because the simple increase or decrease of LDH can have various origins. There are thus different possibilities of interpretation.

If the LDH level is high:

• Anemia

Most often it can be pernicious (also called Biermer’s disease), or hemolytic anemia. In the latter, autoantibodies attach to red blood cells and destroy them, which increases the level of LDH in the blood.

• Cancers: Certain forms of cancer such as neoplasias are also associated with a rapid rise in LDH.
• Infarction: Following a myocardial infarction, associated with damage to the tissues of the heart, an increase in LDH levels is observed within 10 hours. The rate then drops again in the following two weeks.
• AVC (same meaning as infactus)
• Pancreatitis
• Kidney and intestinal diseases
• Mononucleosis
• Pulmonary embolism
• Angina pectoris
• Muscular dystrophy
• Hepatitis (toxic or obstructive)
• Myopathy (depending on the location of the disorder)

If LDH level is low or normal:

In this case it is that no problem is present, or identifiable by this means, in the organism.

Don’t worry: While this list of illnesses may scare those who have had a high LDH result, it is good to remember that other very mundane activities, such as strenuous exercise, can cause a temporary rise in LDH. in the blood.

Conversely, hemolysis (the rupture of red blood cells in the blood) at the time of the test can cause a false positive. The LDH present in the red blood cells will indeed spread, and therefore distort the result.

Following the examination of the LDH level, the results will be sent to your doctor who can discuss them again with you if necessary. If the results indicate the presence of a disorder, then you will simply be referred to the specialist in question.

In the event of cancer, regular monitoring of the LDH level may prove to be a marker of whether or not the cancer has been successful, in order to know whether the target cells are indeed destroyed or whether they attack other parts of the body.