Creatine phosphokinase in long-term dialysis patients.

Of 90 patients undergoing regular dialysis, 42% had elevated levels of creatine phosphokinase (CPK). The BB isoenzyme was not detected, and only one patient had CPK MB. The elevation of CPK MM level did not correlate with values for calcium, phosphorus, calcium times phosphorus product, dry weight, or parathyroid hormone. Elevated levels of the enzyme correlated directly with muscle weakness in male patients and with hypothyroidism (depressed free thyroxin index) and inversely with treatment with vitamin D, supplements. We conclude that high CPK levels in uremia are secondary to skeletal muscle abnormalities and that hypothyroidism and vitamin D, deficiency may contribute to so-called uremic myopathy.