Extreme Creatine Phosphokinase Elevation in a 20-Year-Old Man Participating in a Clinical Trial of Major Depressive Disorder

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Sir: Creatine phosphokinase (CPK) is an enzyme primarilyfound in cardiac and skeletal muscle as well as in brain tissueand the gastrointestinal tract. More specifically, CPK is involvedin the conversion of adenosine triphosphate and creatineto adenosine diphosphate and creatine phosphate via the transferof a high-energy phosphate. Minor elevations of CPK occurroutinely with strenuous exercise, hypothyroidism, and statinassociatedmyopathy.’ ‹