Lactate Dehydrogenase Isozyme 1-Reply

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In Reply.  —Before beginning our study on the use of LD₁ for the diagnosis of myocardial infarction, we also encountered a patient whose condition was diagnosed as myxedema who had an elevated CK-MB level and an LD₁/LD₂ ratio flip, with a normal ECG and no chest pain. We did not have any additional serum remaining to test with the commercially available isoimmune kit (Isomune-LD). However, we would have anticipated an elevated LD₁ concentration. It is therefore likely that hypothyroidism is another clinical entity yielding elevated LD₁. Under ordinary circumstances, angina or myocardial infarction does not usually develop in patients with hypothyroidism; however, some patients may have chest pain and, indeed, even infarct, if replacement therapy is given too vigorously. In these situations, albeit uncommon, the finding of an elevated LD₁ concentration should be interpreted with caution.