Detection of hypothyroid myopathy by measurement of various serum muscle markers--myoglobin, creatine kinase, lactate dehydrogenase and their isoenzymes. Correlations with thyroid hormone levels (free and total) and clinical usefulness.

An accurate and close follow-up of serum levels of thyroid hormones and various muscle markers (myoglobin, creatine kinase and its isoenzymes CK-MB and CK-BB, lactic dehydrogenase, alpha-hydroxybutyric dehydrogenase, etc.) was carried out in 10 hypothyroid patients on replacement therapy. The main muscle markers, creatine kinase and myoglobin, were elevated respectively in 9 and 6 subjects. In 1 male significant CK-MB traces were measured, while in 1 woman significant CK-BB amounts were assayed. Significant correlations between patients' thyroid hormones and the levels of the muscle parameters were found. The rate of normalization of thyroid hormones and muscle markers in relation to replacement therapy was also studied. Myoglobin and creatine kinase have proved to be the best indicators of the hypothyroid myopathy, since they are sensitive for the early detection of muscle involvement due to the metabolic disorder and are closely correlated to the metabolic conditions of patients.