THE METABOLISM OF IODINE IN CEREBROSPINAL FLUID*†

Abstract

L1ITTLE attention has been paid to the penetration of thyroid hormone into cerebrospinal fluid (CSF), although the marked effect of thyroid hormone on the growth, development and function of the central nervous system is well documented. Congenital absence of thyroid hormone may result in the permanently impaired intellect of cretinism. Even adult myxedema results in marked dulling of mental activity, personality changes and occasionally frank psychosis (1). Conversely, overabundance of thyroid hormone, as in Graves' disease, results in mental agitation and occasionally manic or toxic psychosis (2, 3). In myxedema, cerebral blood flow is decreased and cerebral vascular resistance is increased (4, 5). Whether there is a decrease in cerebral oxygen and glucose consumption is in dispute (4, 5). Myxedema causes characteristic changes in the electroencephalogram, consisting of a low voltage, slow frequency, absence of alpha waves, and absence of reaction to light stimulus (5). In hyperthyroidism, cerebral oxygen and glucose consumption are unaltered (4, 6, 7). Increased cerebral blood flow and decreased cerebral vascular resistance have been reported (4, 6), but not by all workers (7). Abnormalities in the electroencephalogram in hyperthyroidism have been demonstrated (8).