Biomarkers are clinical tests that can detect organ dysfunction by measuring substances in blood, urine, or soft tissues. Muscle biomarkers include myoglobin, troponin, and enzymes like creatine kinase. Myoglobin rises early after a heart attack but is not specific, while troponin is specific for detecting heart attacks. Enzyme levels provide information about various muscle and other tissue injuries or diseases. Factors like cell damage, synthesis and clearance rates, and ischemia can influence biomarker concentrations.

1. Muscle Markers
Aron Neupane

2. What are biomarkers?
Biomarkers are clinical laboratory test which is useful in
detecting dysfunction of an organ.
Biomarkers are often measured and evaluated using blood,
urine, or soft tissues to examine normal biological processes,
pathogenic processes, or pharmacologic responses to a
therapeutic intervention.

3. Muscle biomarkers
o Myoglobin
o Troponin
o Enzymes

4. Myoglobin
• Iron and oxygen binding protein found in muscles (identical
to hemoglobin)
• Is raised after myocardial infarction; is not specific and is
raised in various other conditions including muscle injury
• Rises rapidly and falls earlier than CK-MB or troponins
• Negative value will exclude infarction
• Useful in early hours of chest pain

5. Troponin
• Specific markers for myocardial infarction
• not increased in muscle injury
• Troponin I and Troponin T are of importance
• Useful as a marker of any time interval after a heart attack
• High serum level useful for diagnosing MI, muscular dystrophies
Image credit, Sinai EM

6. Enzymes
• Creatine Kinase
• Lactase dehydrogenase
• Aldolase
• Aspartate transaminase

7. Factors affecting serum enzyme levels
• Cell damage
• Rate of enzyme synthesis and clearance
• Enzyme inhibitors
• Myocardial infarction
• Glucose deficiency
• Localized hypoxia (less oxygen)
• Ischemia and Necrosis

8. Creatine Kinase
• Elevated in muscular dystrophies (500-1500 IU/L), CK-MM
• In crush injury, fractures and acute cerebrovascular accidents
• Associated with ATP regeneration from high energy phosphocreatine
in muscles

9. Lactase Dehydrogenase
• Markers of hemolytic anemia
• Hepatocellular diseases
• Muscular dystrophies
• Carcinomas
• Leukemia

10. Aspartate Transaminase
• Normal range of 8-20 U/L
• Elevated in MI, liver disease

11. Aldolase
• Normal serum level is 1.5-7 U/L
• Markers of muscular dystrophies,
• Multiple sclerosis
• Progressive muscular degeneration

12. References
• Textbook of Biochemistry for Medical Students, DM Vasudevan
• Textbook of Biochemistry, Satyanarayana
• Harper’s Illustrated Biochemistry