• Heart
• Liver
• Skeletal Muscle
• Kidney
• Brain 
• Lung

Whenever these structures are injured, either through trauma or disease, LDH can be released into the blood.

Elevations found in:

• Any traumatic injury to any of these structures. 
• Any disease affecting one of these structures.
• Acute myocardial infarction (2-10X normal)
• Pulmonary Infarction (2-4X normal)
• Liver disease 
• Infectious mononucleosis
• Cancer
• Hemorrhagic shock
• Hemolysis
• Hypothyroidism
• Once elevated, the LDH remains elevated for up to 2 weeks days, if the injury is acute. 
• If there is on-going injury, the LDH will remain elevated indefinitely.

LDH Isoenzymes

These five isoenzymes (LD1, LD2, LD3, LD4, and LD5) are found in somewhat different concentrations in different tissues. Some patterns of elevations have been observed:

• LD1 and LD2 are elevated in acute MI, hemolysis and renal infarction.
• Sometimes only LD1 is elevated in acute MI
• When LD1 > LD2, this is strong suggestive evidence of an acute MI
• LD3 elevates with pneumonia and pulmonary infarction
• LD5 elevates in some cancers and liver disease
• A frequent elevation of LDH in patients with malignancy is in LD2, LD3 and LD4.

Normal Values of LDH*

Normal Values of LDH Isoenzymes*

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.