The peripheral blood flow in myxedema as compared with that in hyperthyroidism

Abstract

A method described in previous papers 5, 6 was used. Measurements were made of peripheral blood flow in six patients suffering from myxedema and were compared with similar observations of Stewart and Evans 5 on six subjects who had hyperthyroidism. The myxedematous subjects were studied before treatment and on several occasions during the course of administration of thyroid extract. In addition, certain other measurements of the circulation were recorded. The results may be summarized as follows: 1. 1. In the myxedematous state, when the basal metabolic rate was low, the peripheral blood flow in cubic centimeters per square meter per minute was decreased. With a progressive increase in basal metabolic rate to normal levels during the administration of thyroid extract there was a progressive increase in peripheral blood flow, so that a linear relationship was maintained. On the other hand, as the basal metabolic rate decreased with therapy in the thyrotoxic subjects, there was a progressive decrease in peripheral blood flow; here again, a linear relationship was present. When the peripheral blood flow of the patients of both groups was plotted against basal metabolic rate, the line for the myxedema patients was a rough continuation of the hyperthyroid one; the intercepts with the zero line, however, were slightly different. 2. 2. Since there is a decrease in cardiac output in myxedema and an increase in hyperthyroidism, a smaller than normal amount of blood appears to be available for distribution to the skin in the myxedema patient, and a greater amount in the hyperthyroid one. 3. 3. The circulation time was prolonged in myxedema and short in thyrotoxicosis. When appropriate treatment was instituted, the circulation time returned to normal in each disease. 4. 4. In myxedema the pulse rate and pulse pressure followed roughly the increases in basal metabolic rate and peripheral blood flow. In subjects with hyperthyroidism the fall in pulse rate and pulse pressure roughly paralleled decreases in basal metabolic rate and peripheral blood flow. 5. 5. For the most part, average skin temperature followed the changes in basal metabolic rate and peripheral blood flow in each disease. Similar trends were observed in the temperature of the hands and feet. No direct relationship was established, however, between average skin temperature and the temperature of the hands and feet. 6. 6. No constant or significant changes in rectal temperature were observed in either disease during the several periods of study of each subject. 7. 7. Conservation of heat in myxedema and increased heat dissipation in thyrotoxicosis have been suggested as an explanation for the marked decrease in peripheral blood flow in the former and its increase in the latter.