THE THYROID HORMONE has profound effects on the growth, development, and maturation of the nervous system. Infantile hypothyroidism results in retardation, not only of bodily growth, but also mental development. Eayrs and his associates1 have made extensive studies of the influence of the thyroid hormone on the postnatal morphogenesis of the nervous system in the rat. Thyroidectomy at birth results in a paucity of axodendritic connections, primarily in the neuropil. The perikarya are small in size and more densely packed, and axons and dendrites in the interperikaryonal space are reduced in amount. Associated with these morphological changes are concomitant disturbances in the development of electrical and behavioral activities. The electroencephalograms of neonatally thyroidectomized rats remain low in amplitude, and the appearance of evoked responses is delayed. When it finally appears, the evoked response is characterized by an abnormally long latency and duration and a low amplitude. Innate behavioral
Sokoloff L. Action of Thyroid Hormones and Cerebral Development. Am J Dis Child. 1967;114(5):498–506. doi:10.1001/archpedi.1967.02090260086005
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