A high blood concentration of the enzyme creatine phosphokinase (CPK) usually indicates which of the following conditions?

• A. Liver failure
• B. Diabetes mellitus
• C. Muscle damage
• D. Kidney stones

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of creatine phosphokinase (CPK). CPK is an enzyme found primarily in muscle tissue, including skeletal muscle, cardiac muscle, and to a lesser extent, brain tissue. It plays a key role in energy production by catalyzing the conversion of creatine and adenosine triphosphate (ATP) into phosphocreatine and adenosine diphosphate (ADP).
2. Step 2: Recognize the significance of elevated CPK levels in the blood. When muscle tissue is damaged, CPK leaks into the bloodstream, leading to elevated concentrations. This is often used as a diagnostic marker for muscle injury or stress.
3. Step 3: Eliminate incorrect options based on the physiological role of CPK. Elevated CPK levels are not typically associated with liver failure, diabetes mellitus, or kidney stones, as these conditions do not directly involve muscle damage or the release of CPK into the bloodstream.
4. Step 4: Correlate elevated CPK levels with muscle damage. Muscle damage, whether due to trauma, strenuous exercise, myocardial infarction (heart attack), or certain diseases like rhabdomyolysis, is the most common cause of high blood CPK concentrations.
5. Step 5: Conclude that the correct answer is muscle damage, as it aligns with the physiological mechanism of CPK release into the bloodstream following muscle injury.