LDH is an enzyme synthesized mostly by the liver and found in numerous tissues.  Its role is to remove a hydrogen from a molecule, often part of a detoxification process, which then makes the molecule more receptive to other processes.

Low levels are usually ignored, but may represent under-production in some cases.

Normal levels imply that the containing tissues (liver, kidney, muscle,           ) are functioning properly.

Elevated LDH levels can be a sign of damage (higher elevations) or simply increased metabolic activity (usually lower elevations).

Lactate dehydrogenase – Wikipedia