Thyroid Gland And Brain: Enigma Of Hashimoto’s Encephalopathy

Abstract The versatile clinical manifestations of the Hashimoto’s chronic autoimmune thyroiditis often include psycho-neurological disorders. Although hypothyroidism disturbs significantly the ontogenesis and functions of central nervous system, causing in severe cases of myxoedema profound impairment of cognitive abilities and even psychosis, the behavioural, motor and other psychoneurological disorders accompany euthyroid and slightly hypothyroid cases and periods of Hashimoto’s disease as well, thus constituting the picture of so called “Hashimoto encephalopathy”. The entity, although discussed and explored for more than 50 years since its initial descriptions, remains an enigma of thyroidology and psychiatry, because its aetiology and pathogenesis are obscure. The paper describes the development of current views on the role of thyroid in ontogeny and functions of brain, as well as classical and newest ideas on the aetiology and pathogenesis of Hashimoto encephalopathy. The synopsis of the world case reports and research literature on this disorder is added with authors’ own results obtained by study of 17 cases of Hashimoto’s thyroiditis with schizophrenia-like clinical manifestations. The relation of the disease to adjuvant-like aetiological factors is discussed. Three major mechanistic concepts of Hashimoto encephalopathy are detailed, namely cerebral vasculitis theory, hormone dysregulation theory and concept, explaining the disease via direct action of the autoantibodies against various thyroid (thyroperoxidase, thyroglobulin, and TSH-receptor) and several extrathyroid antigens (alpha-enolase and other enzymes, gangliosides and MOG-protein, onconeuronal antigens) – all of them expressed in the brain. The article demonstrates that all above mentioned concepts intermingle and prone to unification, suggesting the unified scheme of pathogenesis for the Hashimoto encephalopathy. The clinical manifestations, criteria, forms, course, treatment and prognosis of Hashimoto encephalopathy and its comorbidity to other diseases – are also discussed in brief. The relation between Hashimoto encephalopathy and non-vascilitis autoimmune encephalomyelitides of paraneoplastic and non-paraneoplastic origin is emphasized. [1 figure, bibliography – 200 references]