—It is well recognized that CK and other commonly measured serum enzymes can be markedly elevated in patients with hypothyroidism. As we commented, the mechanism for these increases is not completely understood and may represent either increased release from tissue or a decrease in clearance of these enzymes by the liver or at other sites.1 Our data and that of Goldman et al2 clearly demonstrates that the CK elevation can be attributed entirely to a skeletal muscle origin. While it may be possible to qualitatively measure the presence of the isozyme CK-MB, the percentage of this isozyme has always been the same or less than that which would have been expected to be released from skeletal muscle.3 This is similar in the case reported by Strasberg in which the CK-MB level was less than 5%. It could lead to an erroneous clinical impression to attribute
Klein I, Levey GS. Hypothyroidism and Isozyme Elevations-Reply. Arch Intern Med. 1984;144(6):1313–1317. doi:10.1001/archinte.1984.00350180263047
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