LDH isoenzymes (LDH 1 - 5)

LDH-Isoenzymes (also known as LD-isoenzyme, lactic acid dehydrogenase isoenzyme)
This test cannot be requested as a post test

What is the lactate dehydrogenase (LDH) isoenzyme test from serum (LDHISO)
This test measures the level of various lactate dehydrogenase (LDH) isoenzymes in the blood. LDH, also known as lactate dehydrogenase, is a type of protein known as an enzyme. LDH plays an important role in making your body's energy. It is found in almost all tissues of the body.

There are five types of LDH. They are known as isoenzymes. The five isoenzymes are found in varying amounts in tissues throughout the body.

LDH-1: found in heart and red blood cellsLDH-2
: found in white blood cells. It is also found in heart and red blood cells, but in smaller amounts than LDH-1.
LDH-3: found in lung tissueLDH-4
: found in white blood cells, kidney and pancreatic cells, and lymph nodesLDH-5
: found in liver and skeletal muscle.

The test determines the activity of the enzyme lactate dehydrogenase in blood. Lactate dehydrogenase (LD) or lactic acid dehydrogenase is present in all tissue cells. The enzyme is responsible for the conversion of pyruvate to lactate under low-oxygen conditions and is involved in energy production. LD is a so-called tetramer, in which the four protein chains consist of two different subunits: H (heart) and M (muscle). In this way, five combinations can arise and thus five different LDs: LD1 (H4), LD2 (H3M1), LD3 (H2M2), LD4 (H1M3) and LD5 (M4). The different LDs are isoenzymes. The test measures the activity of each isoenzyme. LD1 and LD2 are mainly found in heart muscle tissue and red blood cells; LD3 is somewhat more common in lung tissue, the isoenzymes LD4 and LD5 are mainly found in liver cells and transverse muscle tissue. The enzyme generally remains within tissue cells, but may enter the bloodstream due to disease or damage, increasing the level of LD in the blood. LD isoenzymes can turn into macro-LD in blood by self-poymerization or by antibodies binding to one or more LD isoenzymes. Macro-LDs are less likely to be cleared from the blood and lead to increased enzyme activity in plasma.
When tissues are damaged or diseased, they release LDH isoenzymes into the bloodstream. The type of LDH isoenzyme released depends on which tissues are damaged.

An LDH isoenzyme test is used to find out the location, type and severity of tissue damage. It can help diagnose a number of different conditions, including:

• Recent heart attack
• Anemia
• Kidney Disease
• Liver disease, including hepatitis and cirrhosis
• Pulmonary embolism, a life-threatening blood clot in the lungs

An LDH isoenzyme test is often done as a follow-up to a lactate dehydrogenase (LDH) test. An LDH test also measures LDH levels, but does not provide information about the location or type of tissue damage.

If your results show that the value of one or more LDH isoenzymes are not normal, it probably means that you have some kind of tissue disease or damage. The type of disease or damage depends on which LDH isoenzymes had abnormal levels. Conditions that cause abnormal LDH levels include:

• Anemia
• Kidney Disease
• Liver Disease
• Muscle Injury
• Heart Attack
• Pancreatitis
• Pfeiffer's disease (Glandular fever or mononucleosis infectiosa, more commonly known in the Netherlands as Pfeiffer's disease, a viral infection caused by the epstein-barr virus (EBV), a herpes virus (Human Herpesvirus 4, HHV-4).