Trending
Dear Dr. Roach: My husband is 68. On a blood test in a doctor's office, he had a CPK level of 694. He walks, on average, 6 miles per day, and drinks probably two or three glasses of wine four days a week, and a martini once or twice a week. His kidney and liver function tests are normal. Before the blood test, he walked five days in a row and did yardwork. He has normal aches and pains after working construction for 30 years, but no muscle symptoms, such as weakness, etc.
Should we test further? He was on a statin for eight months but has been off of it for about a year. He takes 25 mg metoprolol for occasional rapid heartbeat, and lisinopril. -- P.L.
Answer: Creatine phosphokinase is a muscle enzyme. There always is some normal muscle breakdown and turnover, so there normally is some level of CPK in the blood. Elevations in blood levels of CPK can represent damage to muscle; however, we are increasingly seeing these results in people with no symptoms (especially since we test people who are taking statins). Many times, the asymptomatic elevations seen in these cases do not represent muscle damage, nor a toxic effect of the medication.
The decision of whether to do further testing depends on how high the elevation is, relative to an individual's normal ("normal" levels in men are about double what they are in women, and blacks' are roughly double those of whites), and a careful history to be sure there aren't unrecognized, subtle symptoms, such as muscle cramping or fatigue. Newer guidelines recommend further evaluation in white men whose level is greater than 500 and black men if greater than 1,200. This is a result of the fact that exercise may cause a larger amount of muscle fiber breakdown in some people than in others. Given his exercise before getting the blood drawn, the first step would be to repeat the test after seven days of minimal exercise. In 70 percent of people, the levels came down into the normal range. If it is still high, then it would be appropriate to consider testing for other causes. Some of them may be surprising, such as low thyroid levels or celiac disease. The metoprolol is a possible cause, as beta blockers have been reported to elevate CPK. However, often no cause is found.