A flipped LD1/LD2 ratio occurs in which scenario?

• A. Injury to LD1 locations (MI, HA, renal infarction)
• B. Pregnancy
• C. Heavy exercise
• D. Liver disease

Answer: (A)

Lactate dehydrogenase has several isoenzymes, with LDH-1 and LDH-2 being the most abundant in blood. In a healthy person, LDH-2 is usually present in a little higher amount than LDH-1. When tissue rich in LDH-1 is damaged, such as heart muscle, more LDH-1 is released into the blood, causing the LDH-1 level to exceed LDH-2. This change is described as a flipped LD1/LD2 ratio and is a classic clue pointing to injury in LDH-1-rich tissues, especially myocardial infarction.

So, injury to LDH-1–rich locations like the heart explains the flipped pattern. In pregnancy, heavy exercise, or liver disease, the pattern does not typically show this flip; they may raise total LD or shift other isoenzyme balances (for example, liver disease tends to raise LDH-5), but the LD1 > LD2 flip is not characteristic of those scenarios.