In liver or skeletal muscle disease, which LD isozymes become predominantly elevated in serum?

In liver or skeletal muscle disease, the LD isozymes that become predominantly elevated in serum are LD4 and LD5. Lactate dehydrogenase (LDH) is an enzyme that exists in five different isoenzymes, which are classified based on their composition of subunits derived from different tissues.

LD4 and LD5 are primarily found in liver and skeletal muscle. When tissue damage occurs in these areas, these particular isozymes are released into the bloodstream, causing an elevation in serum LDH levels. This increase reflects the extent of tissue damage and can be used in clinical diagnostics to help assess liver or muscle disorders.

On the other hand, LD1 and LD2 are primarily associated with the heart and red blood cells, while LD3 has broader tissue distribution but does not specifically indicate liver or muscle damage as poignantly as LD4 and LD5 do in the context of their respective diseases. Therefore, the elevation of LD4 and LD5 in the serum serves as a more specific marker for conditions affecting the liver and skeletal muscle.