The Cerebral Circulation and Metabolism in Hyperthyroidism and Myxedema1

Abstract

In vitro studies (1-5) of the effect of variations in the functional activity of the thyroid gland upon cerebral metabolism have yielded conflicting results; some investigators have found the oxygen consumption of the brain to be increased in experimental hyperthyroidism, and diminished after thyroidectomy; others have not been able to demonstrate a change in the oxygen uptake of brain slices of either hyper-or hypothyroid animals. The introduction of the nitrous oxide method for the determination of cerebral blood flow provided a means of directly measuring cerebral circulatory and metabolic functions in man, and this technique was promptly applied to a study of these functions in human subjects with hyperthyroidism and myxedema. The initial studies in man, however, have also yielded conflicting results, especially with respect to the cerebral circulatory changes in thyroid disorders. Scheinberg (6), and Sokoloff, Wechsler, Balls, and Kety (7) found that the mean cerebral blood flow of a small series of subjects with hyperthyroidism was not significantly different from the mean CBF previously determined in a series of normal young men.Sokoloff, Wechsler, Mangold, Balls, and Kety (8) later reported that the CBF in hyperthyroidism was increased, but attributed this increase to anemia. Scheinberg, Stead, Brannon, and Warren (9) found the mean CBF in subjects with myxedema to be significantly lower than in young normal subjects, an observation in agreement with the findings of Himwich, Daly, Fazekas, and Herrlich (10) who studied the rate of blood flow in cretins by means of a thermostromuhr placed in an internal jugular vein. In 1951, Madison, Sensenbach, and Ochs (11) reported the results 1 Published with permission of the Chief Medical Director, Veterans Administration, who assumes no responsibility for the opinions expressed or conclusions drawn by the authors.of a preliminary study of cerebral circulatory and metabolic functions in hyperthyroidism and myxedema, in which the values for these functions, obtained after euthyroidism had been achieved, served as controls for comparison with pre-treatment findings. Since then, the study has been enlarged to include observations in 22 subjects with hyperthyroidism and 11 with myxedema and forms the basis for the present report. Studies were repeated after euthyroidism had been achieved by treatment in 16 of the 22 hyperthyroid subjects and in 8 of the 11 subjects with myxedema. CLINICAL MATERIAL AND METHODSTwenty-two males with hyperthyroidism whose ages ranged from 24 to 64 years were studied. The diagnosis was established when the characteristic history, physical findings, and laboratory studies clearly indicated the existence of a hypermetabolic state due to overactivity of the thyroid gland. Prior to the institution of definitive therapy, there was a period of observation during which the patients were treated with bed rest, hyperalimentation, supplementary vitamins, and sedation as needed. Just prior to the institution of treatment the initial circulatory studie...

A Correlation of Clinical and Hemodynamic Studies in Patients With Hyperthyroidism With and Without Congestive Heart Failure *

“…The circulatory responses to thyrotoxicosis observed in the seven patients without heart disease or congestive failure (Group IA) at rest were, in general, similar to those described by others (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). The responses of the cardiac output and systemic resistance to mild exercise in these patients were qualitatively similar to healthy persons and the increased blood flow associated with thyrotoxicosis both at rest and during exercise occurred without significant change in right atrial or pulmonary arterial pressures.…”

Effects of prolonged sleep deprivation on local rates of cerebral energy metabolism in freely moving rats

“…The absence of such increases is similar to the situation in clinical hyperthyroidism in which, despite marked increases in total body basal metabolic rate, cerebral oxygen consumption remains unchanged (Scheinberg, 1950;Sokoloff et al, 1953: Sensenbach et al, 1954.…”

Reversible Changes in Brain Glucose Metabolism Following Thyroid Function Normalization in Hyperthyroidism

“…21,22 These early findings were interpreted as the result of decreased vascular resistance, instead of primary changes in brain function. Only decades later did investigators discover significant abnormalities in brain metabolism in the hyperthyroid state.…”