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...

Nor-epinephrine, a pressor amine known to exist normally in the mammalian body, is identical with epinephrine except for the absence of a methyl group in its chemical structure. Since methylation occurs readily in the body, it has been suggested that nor-epinephrine functions chiefly as a precursor to epinephrine (1-5). Nevertheless, it possesses potent pharmacologic properties which differ in many respects from those of epinephrine (6-9). Epinephrine raises systolic blood pressure, increases cardiac output and accelerates the heart rate; it constricts blood vessels in certain areas of the circulatory bed, dilates them in others, with an over-all effect of dilatation and a decrease in total peripheral vascular resistance. Nor-epinephrine increases systolic and diastolic blood pressure, has little or no effect on cardiac output and decreases cardiac rate. It constricts blood vessels in all areas of the circulation in which its effect has been studied.Little is known, however, of the effects of norepinephrine and epinephrine upon the cerebral circulation in man. A clear understanding of their effects on this important segment of the circulation should provide information bearing on a number of physiologic, pathologic, and therapeutic questions.

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