To the Editor.
—In the March Archives (1983;143:434-436), McCoy et al discussed the use of lactate dehydrogenase isozyme 1 (LD1) as a method of rapid assessment in the diagnosis of ischemic heart disease. In their discussion, other pathologic states that can account for elevations of LD1 were mentioned. These included the following: in vivo hemolysis, renal infarction, severe trauma, and isomorphic elevations of total LD. Hypothyroidism is another clinical entity that can elevate LD1, and it should be added to this list.Aber et al1 reported that 17 of the 48 patients with hypothyroidism had LD isozyme patterns identical to that of myocardial infarction, which gradually faded with thyroid replacement therapy and correlated with the time taken to establish a euthyroid state.
Report of a Case.
—I have also observed a patient with hypothyroidism who had a total LD level of 457 units/L (normal, 100-225 units/L)