CREATINE KINASE: NORMAL VALUES, CAUSES AND CONSEQUENCES - MEDICINE - 2025

The creatine kinase (CK), creatine kinase, creatine kinase, creatine phosphokinase (CPK) or fosfocreatín kinase, is an enzyme protein found in various tissues of the human body. Organs with high energy demand are present, such as striated muscle, as well as heart muscle and brain. The enzyme's function is to transfer a phosphate radical -phosphorylation- of creatine to form ATP.

CK is a high molecular weight compound - around 80 KiloDaltons - found within muscle and nerve cells. Inside the cell it is present both in the cytoplasm and in the mitochondria. It is also known as creatine phospho-kinase, or CPK.

By Jfdwolff at en.wikipedia (Transferred from en.wikipedia), from Wikimedia Commons

The CK-MM, CK-MB and CK-BB fractions correspond to isoenzymes present in striated muscle tissue, cardiac and nervous system, respectively.

Although creatine kinase is intracellular, it is found circulating in the blood, available to supply the requirements in the tissues. An increase in CK values ​​in the blood means that the blood has been released as a result of tissue damage.

Injuries to the skeletal and visceral muscles, or to the brain, will cause an elevation of the enzyme in the blood. The consequences derived from this are those derived from the disease that produces it.

What does it consist of?

By Boghog2, from Wikimedia Commons

Creatine kinase favors the process of obtaining rapid energy in the tissues where it is found. The enzyme fulfills its metabolic function at the level of mitochondria and cytoplasm, in the process of muscle or brain ATP exchange. Creatine is the substrate involved in the CK-mediated reaction.

Creatine - discovered in 1832 - is an organic acid that contains nitrogen. The creatine molecule associates with the phosphate radical to form phosphocreatine - a phosphagen - an energy reserve form. CK takes phosphocreatine phosphate to make ATP, necessary for muscle and nerve tissue activity.

In tissues that require a high energy supply, CK facilitates the phosphorylation / dephosphorylation of creatine

Normal values

Creatine kinase is a molecule that is predominantly found within the cell, where it performs its function. However, it is possible to find the enzyme circulating in the blood in a range that does not exceed 200 U / L.

Normal CK values ​​can vary according to factors such as age, sex, race, constitution, and physical activity. In general, in males it is usually slightly higher.

Reference values:

Men: from 15 to 180 U / L.

Women: from 10 to 150 U / L.

Causes of high creatine kinase

CK is an enzyme present in muscle cells –both striated and smooth- and the nervous system. Damage to the tissue of these organs involves cell injury, allowing the release of the enzyme into the blood.

There are multiple causes of increased serum creaticinase levels, predominantly muscular, cardiac and cerebral. Other causes are related to factors that influence the alteration of these organs.

Muscular

Striated muscle can be affected acutely or chronically. Chronic diseases - such as myositis - increase CK levels moderately.

- Trauma.

- Compartment syndrome.

- Parenteral treatment, especially intramuscular or subcutaneous.

- Intense physical exercise.

- Rhabdomyolysis.

- Miosistis.

- Syndromes that occur with muscular dystrophy, such as Duchenne disease or Becker muscular dystrophy.

Cardiac

- Acute coronary accidents, such as angina pectoris and myocardial infarction.

- Cardiomyopathies of different causes.

- Infections, in the case of viral myocarditis.

- Heart failure.

- Pericarditis.

- Defibrillation and electrical cardioversion due to intense muscle contraction, with relative cellular damage.

Nervous system

Any factor capable of inducing damage to nervous tissue produces as a consequence an elevation of enzymes in the blood. The CK-BB fraction is the one that is predominantly affected.

- Infections such as meningitis and encephalitis.

- Cerebrovascular disease, especially of the ischemic type (cerebral infarction).

- Brain tumors.

- Cranio-encephalic trauma including contusion and cerebral edema.

- Epilepsy and seizures. In this case, the BB and MM fractions may rise, due to the intense muscle contraction.

Other causes

Certain organic alterations, diseases and external agents can produce high creatine kinase. This is the product of the influence that certain clinical conditions have on tissue and cellular integrity.

Endocrine system

Thyroid disease - including thyroiditis, hypo, and hyperthyroidism - Addison's disease and Cushing's syndrome.

Neoplasms

Neoplasms or cancerous tumors, due to their ability to alter and destroy tissues, can cause the release and increase of the enzyme. Examples of this are cancer of the digestive tract, prostate, rhabdomyosarcoma, or brain tumors.

Medicines

Both narcotic drugs, alcohol, cocaine and barbiturates as well as commonly used medications. The latter include drugs to lower cholesterol (statins), antibiotics, pain relievers, insulin, and sodium heparin. Thyroid hormone supplements can also raise CK values.

Syndromes

It should be noted that some rare diseases are causes of high CK. Some of them are:

- Reye's syndrome

- Malignant hyperthermia

- Hemolytic syndromes.

- Neuroleptic malignant syndrome.

Consequences of high creatine kinase

Creatine phosphokinase is biologically active in the presence of its substrate creatine. Reactions involving creatine and CK occur within cells. On the other hand, the enzyme found in the blood can be used when required.

CK per se has no biological effects when in free form. However, its presence in amounts above normal is an important indicator of organic damage.

Cardiovascular system

When an injury occurs to the heart muscle, its cells release CK-MB into the bloodstream. The elevation of isoenzymes occurs over several hours. A high MB fraction indicates damage to the myocardium that can cause from organ dysfunction to total failure.

Elevated CK-MB is associated with cardiac pathology and, therefore, arrhythmias, infarction, and heart failure are consequences of myocardial injury.

Striated muscle

The isoenzyme found in skeletal muscle is CK-MM, and its elevation in the blood indicates moderate to severe muscle damage.

Rhabdomyolysis - a condition resulting from strenuous physical exercise - causes enzyme elevation and myoglobin release. Rhabdomyolysis is related to renal tubular damage.

Nervous system

Any entity or pathology that affects the central nervous system, both traumatic and infectious, will cause an elevation in the blood of the BB fraction of creatine kinase.

Although it is not a routine analysis, its presence indicates the presence of organic lesions and can even predict its evolution.

References

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