Lactate dehydrogenase: (LDH) An enzyme that catalyzes the conversion of lactate to pyruvate. This is an important step in energy production in cells. Many different types of cells in the body contain this enzyme. Some of the organs relatively rich in LDH are the heart, kidney, liver, and muscle.
As cells die, their LDH is released and finds its way into the blood. Normal LDH levels vary with age, being higher in childhood due to bone growth. Analysis of LDH has not been standardized and normal ranges vary greatly between laboratories. Generally, the upper limit of normal for adults is in the range of 200 units/liter.
Nearly every type of cancer, as well as many other diseases, can cause LDH levels to be elevated. Therefore, this marker cannot be used to diagnose a particular type of cancer. LDH levels can be used to monitor treatment of some cancers, including testicular cancer, Ewing's sarcoma, non-Hodgkin's lymphoma, and some types of leukemia. Elevated LDH levels can be caused by a number of noncancerous conditions, including heart failure, hypothyroidism, anemia, and lung or liver disease.