Lactate Dehyderogenase, Serum

Lactate dehydrogenase is an enzyme which plays an essential role in the production of energy from glucose. It is present in all the cells of the body, with the highest concentrations being in the cells of heart, lungs, muscles, liver, kidneys, and RBCs. Normally, only a small amount of the enzyme is found in the serum outside blood cells. However, in certain conditions of damage to the cells, lactate dehydrogenase is secreted out of the cells into the serum, where its concentration rises. Thus, the Serum Lactate Dehydrogenase Test is a nonspecific test that helps to determine the presence of conditions causing tissue damage somewhere in the body. Further tests are performed to identify the exact cause and location of these conditions.

The total lactate dehydrogenase in the body consists of five different forms of the enzymes (isoenzymes) named LDH-1 to LDH-5. The isoenzymes are present in different concentrations in different organs of the body. For example, LDH-1 and LDH-2 are most abundant in the cells of the heart, while LDH-5 is most abundant in the liver. Although the total LDH levels indicate tissue damage somewhere in the body, testing for the different isoenzymes can help identify the location of such damage.

Lactate dehydrogenase is also secreted into other body fluids in case of damage to the body tissues. It is also produced by bacteria and can be thus used to help identify bacterial meningitis.