[Assay of serum creatine phosphokinase in primary hypothyroidism. Comparison with other thyroid gland function tests in 32 cases. Value of isoenzyme studies].

Serum-creatine phosphokinase levels were measured in 32 cases of primary hypothyroidism in adults and compared with the results of other thyroid function test. C.P.K. elevation appeared to be almost completely uniform (31 out of 32 cases) and marked, reaching six times the normal value. This elevation is more marked in 18 myxoedematous patients than in 14 with those with hypothyroidism of mixed aetiology. Close correlation does not seem to exist between the elevation of C.P.K. and the lowering of serum thyroxine. The elevation of C.P.K. above the upper limits of normal seemed more constant than lengthening of the achilles reflex time, a rise in serum cholesterol, or a rise in other enzymes of muscular origin, such as the glutampopyruvic and glutamo-oxalocetic transaminases, lactodehydrogenase and hydroxybutyric dehydrogenase. In 8 cases of hypothyroidism, the isoenzymic study of serum C.P.K. by electrophoresis on cellulose acetate confirmed that the molecular structure was of the muscle type MM. The advantage of such a study shows that a structure MB found in the case of myocardial infarction in a patient with hypothyroidism deserves to be stressed.