Lactate dehydrogenase (LDH) is an enzyme that is involved in the process of glucose oxidation and the formation of lactic acid. In a healthy person’s body, LDH does not accumulate, but collapses and is eliminated in a natural way. However, there are a number of diseases and pathological conditions that are characterized by a moderate or significant increase in LDH in the blood.
What is LDH?
LDH is found in almost every organ but its greatest concentration is present in the liver, skeletal muscle and myocardium. The enzyme has five isoenzymes (modifications), which differ from each other in structure, as well as in their specificity – each of them is concentrated in a specific organ.
- LDH-1 predominates in the tissues of the heart muscle and brain;
- LDH-1 and LDH-2 are contained in blood cells (erythrocytes, platelets) and kidneys;
- LDH-3 is an enzyme of the skeletal muscles, lungs, thyroid and pancreas, adrenal glands and spleen;
- LDH-4 is found in the same tissues as LDH-3, as well as in the liver, placenta, male germ cells and granulocytes;
- LDH-5 is characteristic of the liver and skeletal muscles, as well as for organs containing LDH-4.
Due to the fact that the concentration of LDH in the blood increases with diseases that are accompanied by damage to tissues and cells, this enzyme is a very important diagnostic marker. The analysis that determines the concentration of LDH in the blood, in combination with other tests is often used to identify a variety of disorders in the body. Such a study is appointed to determine the following diseases and pathologies:
- Diagnosis of myocardial infarction, heart and lung diseases with complaints of severe chest pain;
- Diagnosis of malignant neoplasms;
- Diagnosis of muscle pathologies;
- Monitoring the treatment of cancer patients and the course of certain diseases;
- Comprehensive examination of patients.
The norm of LDH in a healthy person’s body depends primarily on its age: so, at the beginning of life, its concentration rises, and begins to decline with age. Reference values:
The level of LDH can be increased in the patient’s blood in the following diseases and pathological conditions:
- Myocardial infarction: an increase in the concentration of LDH in the blood during myocardial infarction is observed in the first 36-55 hours, after which the level of the enzyme is maintained for 3-10 days
- Congestive heart failure
- Lung heart attack: Lactate dehydrogenase is elevated already on the first day after the appearance of pain in the chest.
- Pathology of the kidney (kidney infarction, pyelonephritis and
- Heavy physical exertion prior to analysis
- Alcohol consumption
- The patient has a prosthetic heart valve that is able to cause hemolysis of erythrocytes
- The use of electric pulse therapy on the eve of the study
- Some diseases of the skin
- Medications that can increase LDH levels: acetylsalicylic and valproic acid, anesthetics, anabolic steroids, codeine, non-specific anti-inflammatory drugs, sulfonamides, penicillin, insulin, caffeine.
When myocardial infarction peak enzyme concentration is observed for 3-4 days, and remains at the same level for 10 days. In addition, in this case, the patient has a significant increase in the level of LDH-1. If a person has not suffered a heart attack, but an attack of angina, the analysis will show the absence of destruction of cardiac cells.
The main difference between pulmonary embolism and heart attack is that in the first case, an increase in LDH is accompanied by an increase in bilirubin level and normal AST.
When inflammation of the brain membranes (viral meningitis), an increase in LDH is negative and indicates the development of encephalitis.
In case of serious liver pathologies, the concentration of LDH increases and remains unchanged for a long time.
In the diagnosis of any disease it is very important to determine the activity of an isoenzyme in order to determine the localization of the pathological process. In particular, in patients with acute leukemia, an increase in the activity of LDH-2 and LDH-3 is observed, while in liver diseases the concentration of LDH-4 and LDH-5 increases. Malignant neoplasms are characterized by a significant increase in the concentration of the isoenzymes LDG-3, LDH-4 and LDH-5.
The level of LDH in the blood of oncological patients decreases with effective therapy, therefore this marker is used to monitor the dynamics of treatment.
A decrease in LDH is characteristic of the following conditions:
- Elevated levels of urea (uremia) and oxalates in the patient’s body
- Taking certain medicines: ascorbic acid, dofibrate, amikacin, naltrexone, anticonvulsants