Makindo Medical Notes

Related Subjects: |Ferritin |CEA |ESR |CRP |ALP |LDH |HbA1c |Alpha Fetoprotein |Anti-Hu ab |Biochemical Lab values

LDH is an enzyme found in various tissues. High levels generally indicate tissue breakdown and are elevated in conditions such as infections, haemolysis, cancers, and myocardial infarction.

About Lactate Dehydrogenase (LDH)

• Isoforms: LDH has five isoforms (LD1 to LD5), each associated with different tissues:
  • LD1: Primarily found in the heart and red blood cells.
  • LD2: Also found in the heart and red blood cells but in higher concentrations in healthy individuals.
  • LD3: Found in the lungs and other tissues.
  • LD4: Associated with the kidneys and pancreas.
  • LD5: Primarily found in the liver and skeletal muscles.
• Function: LDH catalyzes the reversible conversion of pyruvate to lactate during anaerobic glycolysis, playing a key role in cellular energy production under low oxygen conditions.
• In many cancers, a raised LDH is considered a poor prognostic indicator, reflecting high metabolic activity and tissue turnover.
• In myocardial infarction (MI), LDH1 is typically greater than LDH2 (a "flip" in the ratio), though troponin is now the preferred test for cardiac injury.

Conditions Associated with Elevated LDH

Elevated LDH levels are indicative of increased cell turnover or tissue breakdown. Common conditions include:

• Myocardial Infarction (MI): LDH rises within 24-48 hours, peaking at 48-72 hours and remaining elevated for up to 10 days post-MI.
• Pneumocystis Pneumonia (PCP): Elevated LDH is often seen in PCP infections, particularly in immunocompromised patients.
• Haemolysis: In conditions causing red blood cell destruction (e.g., autoimmune haemolytic anaemia), LDH is elevated due to rapid cell breakdown.
• Stroke: Elevated LDH may reflect tissue damage in ischemic or hemorrhagic stroke.
• Malignancy: Elevated LDH is often seen in rapidly proliferating cancers such as lymphoma and testicular cancer. LDH levels can also help monitor disease progression and response to treatment.
• Infectious Mononucleosis: LDH levels may be elevated due to systemic involvement and tissue breakdown.
• Pancreatitis: Acute pancreatitis can cause elevated LDH due to pancreatic cell damage.
• Liver Disease: LDH is elevated in liver ischaemia, hepatitis, and other conditions affecting hepatocytes.
• Renal Disease: Certain types of kidney disease can result in elevated LDH due to renal cell injury.
• Muscle Damage: Elevated LDH is seen in muscle trauma, rhabdomyolysis, and conditions causing muscle breakdown.