Your body's muscle tissue contains several enzymes, which are catalysts that cause chemical reactions. Your muscles require chemical reactions to supply them with energy, help them repair damage and help them function. High muscle enzymes in your blood can mean that muscle cells have been damaged. High muscle enzymes can also occur because of muscle-wasting disorders or because of damage to another organ that contains some of the same enzymes as your muscles, such as the liver. If you have high muscle enzyme levels in your blood, your doctor will evaluate any symptoms you have and perform other necessary tests to find out the cause.
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Commonly tested muscle enzymes include creatine phosphokinase, serum glutamic oxaloacetic transaminase, lactate dehydrogenase and aldolase. Creatine phosphokinase makes possible a chemical reaction that converts creatine into phosphate, which is a quick energy source for your muscles. Serum glutamic oxaloacetic transaminase, which is also called SGOT or aspartate aminotransferase, is necessary for your body to process amino acids and use them to build the proteins in your muscle tissue. Lactate dehydrogenase (LDH) is present in all of your body's cells, including your muscle cells. Your body uses aldolase to metabolize amino acids.
Doctors test your muscle enzyme levels to screen for medical conditions that cause elevated muscle enzymes. Many causes of high muscle enzymes are relatively harmless. For example, common muscle strains can cause your creatine phosphokinase levels to elevate. Your SGOT levels may also elevate because of any type of muscle damage. Elevated lactate dehydrogenase levels may indicate cell damage of any kind. Your doctor may test your aldolase levels if you are experiencing weakness to determine whether the problem is in your muscles or your nerves, because muscle problems cause elevated aldolase and nerve problems do not.
Sometimes elevated muscle enzymes help doctors diagnose dangerous medical conditions. High aldolase levels occur in muscular dystrophy or because of a heart attack, hepatitis, polymyositis or mononucleosis. Some types of malignancy, such as cancer of the pancreas, prostate or liver, cause aldolase to elevate. Conditions including liver disease, stroke, mononucleosis, hemolytic anemia or muscular dystrophy can cause elevated LDH. Elevated SGOT may indicate liver problems or a recent heart attack. High creatine phosphokinase may occur during a heart attack or may indicate stroke, muscular dystrophy, myocarditis or lung tissue damage. Very high levels of muscle enzymes can indicate a large amount of muscle tissue damage, also called rhabdomyolysis, which is potentially life-threatening because proteins from broken-down muscle tissue can collect in the kidneys and cause kidney damage or acute renal failure.
If your doctor suspects a heart attack, she will probably perform an electrocardiogram, abbreviated as EKG or ECG, to measure the electrical signals in your heart muscle. If she suspects a stroke, she may order a magnetic resonance imaging scan or a brain angiogram. Your doctor may perform an MRI, ultrasound or biopsy of your liver if she suspects liver disease. A muscle biopsy or genetic testing may be necessary to screen for muscular dystrophy. She may order a blood test to check for antibodies to the Epstein-Barr virus if she suspects mononucleosis.
REFERENCES & RESOURCES
- "Exercise Physiology: Nutrition, Energy, and Human Performance"; William D. McArdle, Frank L. Katch, Victor L. Katch; 2009
- MedlinePlus Medical Encyclopedia: Aldolase Test
- MedlinePlus Medical Encyclopedia: Lactate Dehydrogenase Test
- MedlinePlus Medical Encyclopedia: Creatine Phosphokinase Test
- The Myositis Association: Blood Tests
- Muscular Dystrophy Association: Facts About Metabolic Diseases of Muscle