LDH Test

LDH Test (Lactate Dehydrogenase)

LDH Test, LDH is basically an intracellular enzyme. LDH is present in almost all tissues of the body. Its increase in the body indicates tissue damage. High levels of LDH are present in skeletal muscle cells, heart liver, and Red blood cells. A low amount of LDH is present in the kidneys, spleen, brain, Pancreas, and lungs.

• LDH is also called the LD test
• The full form of LDH or LD is Lactate Dehydrogenase
• LDH is also called Lactic acid Dehydrogenase

LDH is a tetrameric enzyme composed of four subunits. There are five different isoenzymes (LDH-1 to LDH-5) that can be found in various tissues, with each having a slightly different makeup of these subunits. The specific LDH isoenzyme composition in the blood can provide information about the source of tissue damage or injury when elevated levels are detected. For example, LDH-1 is found mainly in the heart, while LDH-5 is more prevalent in the liver.

Clinical significance: LDH is often measured as part of a blood test to assess tissue damage or various medical conditions. Elevated levels of LDH in the blood can indicate cellular damage or injury, and this can be seen in various situations, including:

1. Heart attack (myocardial infarction): Elevated LDH-1 levels can suggest damage to heart muscle.
2. Liver disease: Increased LDH-5 levels may indicate liver damage or disease.
3. Muscle injury: Muscular trauma or diseases like muscular dystrophy can lead to higher LDH levels.
4. Hemolysis: The breakdown of red blood cells can release LDH into the bloodstream.
5. Certain cancers: LDH levels may be elevated in various types of cancer, and monitoring LDH levels can help in cancer diagnosis and treatment.
6. Infections: Some infections can cause LDH levels to rise as a result of tissue damage.
7. Other conditions: LDH levels can be affected by a range of medical conditions, so elevated LDH is not specific to any one disorder.

Isoenzymes of LDH

Isoenzymes are groups of two or more enzymes with identical functions but different structures.

There are 5 isoenzymes of LDH:

• LDH 1 Present in heart and Red blood cells
• LDH 2 Reticuloendothelial system
• LDH 3 Lungs
• LDH 4 Spleen, Placenta, and Kidneys
• LDH 5 Skeletal Muscle and Liver

Function of LDH

It helps in the process in which glucose present in food is changed into usable energy for our cells.

Normal Range of LDH and LDH Isoenzymes

• Total LDH 140 to 280U/L
• LDH 1 17 to 27%
• LDH 2 28 to 38%
• LDH 3 17 to 28%
• LDH 4 5 to 15%

Specimen Collection for LDH Test

1. Collect 3 to 5 ml of blood in a Gel tube
2. Centrifuge the blood sample and use the serum for the test

Causes of High LDH in blood

1. Prostate Cancer
2. Heart Attack
3. Hypothyroidism
4. Skeletal Muscle Disease
5. Trauma
6. Bone Metastases
7. Liver Cancer and Damage
8. Acute Pancreatitis
9. Billary Obstruction
10. Congestive Heart Failure
11. Pneumonia
12. Fractures
13. Hemolytic Anemia

NOTE

• Normally in labs, LDH is measured as total LDH in patients’ serum
• So measuring the isoenzymes can help to differentiate the source of the elevated total LDH because every isoenzymes is specific for different tissues.