THE PULMONARY ABNORMALITIES IN MYXEDEMA*†

Abstract

Twenty-six patients with myxedema were studied before treatment and 21 were restudied after treatment with desiccated thyroid or triiodothyronine. Sixteen patients had myxedema but no lung disease, 6 patients had myxedema and were obese, and 4 patients had myxedema and lung disease. The lung volumes were normal in the patients with myxedema only. Obese patients with myxedema had moderate reduction in inspiratory capacity, expiratory reserve volume, vital capacity, residual volume and total lung capacity, probably on the basis of obesity. Four of 6 patients with myxedema and obesity had alveolar hypoventilation. Lung disease and disease of the bony thorax were absent. The authors suspect that the muscles of respiration or neuromuscular coordination are involved. The maximal breathing capacity was reduced in patients with myxedema and increased after therapy. This suggests the presence of a "muscular" lesion which is reversible. The diffusing capacity of the lungs for CO was reduced in patients with myxedema and increased slowly but significantly after therapy. The best explanation for this is pulmonary capillary involvement, either a thickened alveolar capillary membrane or a reduction in the pulmonary capillary bed, or both.