Sodium, potassium and water metabolism in myxoedema.

In a combined radioactive isotope study, Na, K, bromine space and total body water were measured in a group of fourteen hypothyroid subjects. These were compared with a ‘control’ group. Total body water and Na were found to be increased in the hypothyroid subjects. In seven subjects, the measurements were repeated after treatment with thyroid hormone. Most of the subjects lost weight and showed a decrease in total body water, but changes in Na, K and bromine space were variable. The cause and nature of the fluid and electrolyte retention in myxoedema are discussed and reasons are advanced for the apparent inconsistencies in the results obtained in this and other studies.