[Myocardial ultrastructure in experimental myxedema]

Total thyroidectomy was performed in 18 rabbits and the material obtained analysed. Nine rabbits with pseudo thyroidectomy served as controls. Basal metabolism, levels of cholesterol, lipoproteins, phospholipids, and ionic blood composition were studied in the experimental animals before the operation and during various periods following the operation; the ultrastructure of the myocardium in the course of myxedema was also studied. Drastic changes in the contractile structures, which apparently were a substrate of cardiac weakeness in this pathologic state, are described.