LDH has 5 main isoenzymes (LD1 through LD5) which are present in different organs in different amounts. These can be separated by electropheresis. The relative amount of each isoenzyme may help to identify where an isoenzyme is coming from.
Each isoenzyme is a combination of 4 subunits, with each subunit one of two monomers (A or B. For example, LD1 is AAAA and LD5 is BBBB.
Disorder
LDH Isoenzyme Pattern
myocardial damage
elevated LD1 and LD2, especially when LD1 > LD2
hemolysis
elevated LD1 and LD2
germ cell tumor
elevated LD1
CNS damage
LD2, LD3, LD4
pulmonary injury
LD3
multiple myeloma
LD3
skeletal muscle
LD5
liver
LD5
platelets
LD2, LD3
Specimens should not be hemolyzed since this may obscure the underlying patterns.
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