What causes an elevation in creatinine kinase (CK) levels?

From the Guidelines

Elevation in creatinine kinase (CK) levels is primarily caused by damage to muscle tissue, with the most common causes including strenuous exercise, muscle trauma, and medications such as statins. The pathophysiological background of an exercise-induced CK increase is complex and not yet fully understood 1. However, it is well established that mechanical stress placed on the muscle results in membrane damage, allowing the large CK molecule to leave the cell and enter the bloodstream 1. Some of the key factors that contribute to elevated CK levels include:

• Strenuous exercise, particularly those involving eccentric contractions 1
• Muscle trauma, such as muscle strains or tears
• Medications, particularly statins like atorvastatin and simvastatin 1
• Muscle diseases, such as muscular dystrophy and polymyositis
• Heart attacks, seizures, and rhabdomyolysis
• Alcohol abuse, certain infections, and electrolyte abnormalities When muscle cells are damaged, they release CK into the bloodstream, which is why CK serves as an important marker for muscle injury. The degree of elevation often correlates with the extent of muscle damage - minor elevations (2-5 times normal) may occur with exercise, while severe elevations (>10 times normal) suggest significant muscle breakdown 1. It is essential to identify the underlying cause of elevated CK levels, stop any contributing medications if possible, ensure adequate hydration, and seek medical evaluation, especially if levels are significantly elevated or accompanied by muscle pain, weakness, or dark urine. In clinical practice, it is crucial to consider the potential for myopathy and rhabdomyolysis when prescribing statins, particularly in combination with other medications that may increase the risk of muscle damage 1. Overall, the management of elevated CK levels requires a comprehensive approach that takes into account the underlying cause, the degree of elevation, and the presence of any accompanying symptoms or signs of muscle damage.

From the Research

Causes of Elevated Creatinine Kinase (CK) Levels

Elevated CK levels can be caused by various factors, including:

• Physical activity and exercise, particularly strenuous or prolonged activities such as ultradistance marathon running, weight-bearing exercises, and downhill running 2
• Muscle damage or injury, which can occur due to physical training or other forms of muscle stress 2, 3
• Muscle diseases, such as myopathy, which can cause persistently elevated CK levels 2
• Peripheral neuropathy, which has been associated with elevated CK levels and muscle cramping 4
• Nephrotic syndrome, a protein-wasting disorder that can lead to increased susceptibility to muscle injury and elevated CK levels after exercise 5
• Other factors, such as age, gender, race, and climatic conditions, which can also influence CK levels 2

Exercise-Induced CK Elevation

Exercise-induced CK elevation is a common phenomenon, particularly after eccentric or high-intensity exercise 2, 3. Studies have shown that:

• CK levels can increase significantly after exercise, with peak levels often occurring 24-48 hours after exercise 2, 3
• The magnitude of CK elevation can vary widely between individuals, depending on factors such as fitness level, exercise intensity, and muscle damage 2, 3
• Despite marked CK elevations, renal function is not typically impaired in healthy individuals 3

Clinical Significance of Elevated CK Levels

Elevated CK levels can have important clinical implications, including:

• Diagnosis of muscle damage or disease, such as myopathy or rhabdomyolysis 2, 6
• Monitoring of muscle injury or disease progression 2
• Identification of individuals at risk for muscle damage or disease, such as those with nephrotic syndrome or peripheral neuropathy 4, 5