Lactate dehydrogenase (LDH) is an enzyme whose levels in the blood indicate tissue damage. Doctors measure LDH to diagnose conditions like heart failure, anemia, or liver disease.
LDH helps convert lactate to pyruvate during metabolism. When cells are damaged, they release LDH into the bloodstream. Higher LDH levels suggest greater tissue injury.
| Test Type | Purpose | Normal Range |
|---|---|---|
| Total LDH | General screening | 105-333 IU/L |
| LDH Isoenzymes | Pinpoint specific organ damage | Varies by isoenzyme |
Unlike markers for specific organs (like troponin for the heart), LDH is nonspecific. This means it detects general cell damage rather than targeting one organ system. For example, LDH rises in both heart attacks and muscle tears, while troponin only appears in cardiac events.
In my work reviewing lab reports, I noticed LDH often appears alongside other markers. A patient with suspected liver disease might show high LDH and elevated liver enzymes, confirming the diagnosis.
Some believe LDH only indicates heart problems. However, it reflects damage anywhere in the body. Others assume normal LDH rules out serious issues, but false negatives occur if testing happens too soon after injury.
According to the Mayo Clinic, LDH levels typically return to normal within 7-10 days of resolving the underlying issue. Persistent elevation suggests ongoing damage.
Doctors request LDH tests when symptoms suggest tissue damage but the source is unclear. For instance, unexplained fatigue might trigger LDH testing to check for anemia or muscle disorders.
The American Cancer Society notes that LDH is sometimes included in cancer workups, as many tumors release this enzyme. However, it's not used alone for diagnosis due to its lack of specificity.