The LDH isoenzymes panel measures different forms of lactate dehydrogenase (LDH), an enzyme involved in the body’s energy production. Lactate dehydrogenase helps convert sugar into energy, especially when oxygen levels are low, such as during intense exercise or when tissues are injured. However, LDH is not a single enzyme. It exists as five slightly different forms called isoenzymes, labeled LDH-1 through LDH-5, each found more heavily in specific parts of the body.
When tissues are damaged, whether from a heart attack, liver disease, anemia, lung injury, or even cancer, these cells break apart and release their specific LDH isoenzymes into the bloodstream. By measuring which isoenzymes are elevated, doctors can often pinpoint where in the body the damage has occurred.
For example, a pattern with very high LDH-1 compared to LDH-2 is often a sign of a heart attack or hemolytic anemia (a condition where red blood cells break down too quickly). High LDH-5 suggests liver disease or muscle injury. If LDH-3 is dominant, it may point to lung disease or certain cancers like lymphoma. Because LDH isoenzymes give a more detailed picture than a total LDH test alone, they are sometimes used when a doctor needs to dig deeper into an unexplained elevation in total LDH levels.
However, LDH isoenzyme patterns are not completely specific. Other conditions like infections or generalized inflammation can also shift the isoenzyme patterns. Additionally, a few factors can interfere with results: vigorous exercise before the test, recent surgery, or even hemolysis (breakdown of red blood cells during blood collection) can all falsely elevate LDH levels.
Overall, the LDH isoenzymes panel can be a helpful tool for distinguishing between different types of tissue damage when used alongside other tests and a thorough clinical evaluation.
