Lactate Dehydrogenase (LDH) Isoenzymes Test

The Lactate Dehydrogenase (LDH) Isoenzymes test measures the level of the different lactate dehydrogenase (LDH) isoenzymes in the blood. LDH, also known as lactic acid 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 the body's tissues.

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. This test can help your provider find out the location and cause of your tissue damage.

The five isoenzymes are found in different amounts in tissues throughout the body:

• LDH-1: found in heart and red blood cells
• LDH-2: found in white blood cells. It is also found in heart and red blood cells, but in lesser amounts than LDH-1.
• LDH-3: found in lung tissue
• LDH-4: found in white blood cells, kidney and pancreas cells, and lymph nodes
• LDH-5: found in the liver and muscles of skeleton