Which LDH isoenzyme pattern is most associated with liver and skeletal muscle involvement?

Which LDH isoenzyme pattern is most associated with liver and skeletal muscle involvement?

• A. LDH1/LDH2
• B. LDH3
• C. LDH5
• D. LDH4

Answer: (C)

LDH consists of five isoenzymes (LDH-1 through LDH-5), each with tendency to be more abundant in certain tissues. In liver and skeletal muscle, the dominant form is LDH-5 (the M4 form). When these tissues are damaged, they release LDH into the blood, and LDH-5 becomes relatively elevated compared with the other isoenzymes. Therefore, a serum pattern with a high proportion of LDH-5 is most associated with liver and skeletal muscle involvement. In contrast, LDH-1 and LDH-2 are more prominent in heart tissue, LDH-3 is associated with lung tissue, and LDH-4/LDH-5 patterns reflect liver and muscle involvement, with LDH-5 being the strongest indicator for those tissues.

LDH consists of five isoenzymes (LDH-1 through LDH-5), each with tendency to be more abundant in certain tissues. In liver and skeletal muscle, the dominant form is LDH-5 (the M4 form). When these tissues are damaged, they release LDH into the blood, and LDH-5 becomes relatively elevated compared with the other isoenzymes. Therefore, a serum pattern with a high proportion of LDH-5 is most associated with liver and skeletal muscle involvement.

In contrast, LDH-1 and LDH-2 are more prominent in heart tissue, LDH-3 is associated with lung tissue, and LDH-4/LDH-5 patterns reflect liver and muscle involvement, with LDH-5 being the strongest indicator for those tissues.