Contents
Myoglobin is the main globular protein of striated muscles (skeletal and heart muscle). It is a single polypeptide chain, similar in structure to the structure of hemoglobin. It is a reservoir of oxygen in the muscles.
What is Myoglobin?
Myoglobin is a marker, a protein and a substance that enters the blood when muscles (the skeletal body and also the heart muscle) are damaged. The function of myoglobin is to store and supply oxygen to the muscles so that they can produce the energy needed for contraction. Protein (myoglobin) is released from the blood when any muscle is damaged. It can also get into the urine. The myoglobin test is performed, inter alia, in the case of suspected myocardial infarction. However, taking into account that myoglobin is released into the bloodstream almost simultaneously with the creatinine kinase and the muscle fraction of the kinase – it is not very important in confirming the infarction. The value of myoglobin is critical only when it is difficult to make an accurate diagnosis. If the enzyme levels do not rise four hours after the onset of symptoms, a heart attack can be completely ruled out.
When do we do the myoglobin test?
Measurement of myoglobin is recommended in the following cases.
1. Suspicion of myocardial infarction (myoglobin is one of the heart markers getting into the blood as a result of myocardial damage). The myoglobin test is good for diagnosing a “fresh” heart attack, not the few hours after that.
2. Skeletal muscle damage.
3. Assessment of reperfusion treatment in acute myocardial infarction.
4. Urine myoglobin testing is recommended for people who have severely damaged skeletal muscles (its concentration reflects the degree of damage).
5. Assessing the risk of kidney failure. A high increase in myoglobin is toxic to the kidneys.
Myoglobin – study
Material for the study of myoglobin: serum.
Preparation for the test: no preparation required.
The course of the myoglobin test: one-time blood sampling from a vein in the arm.
Time to wait for the result: 1 hour.
Comments:
- Myoglobin is released into the serum in the event of necrosis of myocardial cells or damage to skeletal muscles.
- Myoglobin levels increase 1-4 hours after myocardial infarction, peaking after 4-8 hours and normalizing after 24 hours.
- Increased levels of myoglobin are also found as a result of cell hypoxia, injury, and rhabdomyolysis (breakdown of skeletal muscle cells).
- Myoglobin is an early marker of muscle cell damage. Currently, however, it is rarely used in the diagnosis of myocardial infarction, because its concentration also increases in renal failure and skeletal muscle damage.
- However, due to the early rise in concentration and the rapid disappearance of after a myocardial infarction, myoglobin assay is useful in identifying “infarction build-up”, the next episode of necrosis of myocardial cells immediately following a myocardial infarction.
What are the norms for myoglobin?
- blood: less than 50 ng / ml,
- urine: up to 17 µg per 1 g of creatinine.
How to correctly interpret the results of myoglobin tests
There are no standard reference ranges for myoglobin. This is due to the fact that the values depend on several factors, e.g. the determination method, gender, age and the studied population. Thus, the test result may have different meanings in different laboratories. In any case, the result should be consulted with a doctor.
It is worth noting that the concentration of myoglobin is normal in blood absolutely excludes a heart attack.
Most often, high levels of myoglobin in the blood and urine means muscle damage that results from:
- from infection,
- from intense physical exertion,
- from injuries (e.g. crushing),
- from the use of intramuscular injections,
- from myositis,
- from certain genetic diseases in which skeletal muscles are damaged,
- from certain diseases of skeletal muscles, among which we mention: myopathy, rhabdomyolysis and muscular dystrophy,
- from epilepsy.
Additional tests, such as a troponin test, need to be performed to locate the lesion.
In addition to the aforementioned ailments, a high level of myoglobin can mean: risk of kidney damage. High myoglobin can result from diabetic coma, hypokalemia, Conn’s syndrome, hypophosphataemia, hypernatraemia, hypothyroidism, alcohol intoxication, and the use of certain medications or drugs.
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