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Papel nutricional nas doenças autoimunes da tiróide
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As doenças autoimunes da tiroide (DAT) são um grupo de doenças inflamatórias que afetam a glândula tiroideia, caracterizando-se por uma resposta imunológica anómala contra antigénios tiroideus. As duas formas mais comuns de DAT são a tiroidite de Hashimoto e a Doença de Graves. A tiroidite de Hashimoto caracteriza-se por um hipotiroidismo devido à destruição autoimune do tecido tiroideu e envolve a produção de autoanticorpos contra a tiroglobulina e a peroxidase tiroideia. Por outro lado, a doença de Graves é caracterizada por um hipertiroidismo resultante do estímulo excessivo da tiróide por autoanticorpos que se ligam aos recetores da TSH à superfície das células foliculares da tiroide.
Estudos recentes sugerem haver uma relação entre as DAT e alguns fatores nutricionais e/ou dietéticos, os quais parecem exercer algum efeito no processo inflamatório. Alguns exemplos são o iodo, a vitamina D, o ferro, o selénio e o glúten. O iodo, presente em alimentos como o peixe, está diretamente envolvido na síntese das hormonas tiroideias na forma de ião iodeto, sendo um elemento de presença crucial. Quer a insuficiência como o excesso de iodo têm efeitos negativos na tiroide. A vitamina D pode ser obtida por via oral, estando presente na dieta nas formas de vitamina D2 e D3, ou por via cutânea, através da exposição solar, que estimula a produção de vitamina D3 na pele. Alguns estudos sugerem uma relação entre a falta de vitamina D e o desenvolvimento de problemas imunológicos. O selénio é um mineral encontrado em grandes concentrações na tiroide, onde desempenha funções importantes na homeostase redox celular e na regulação da síntese das hormonas tiroideias. O ferro parece desempenhar igualmente um papel importante na produção das hormonas T3 e T4, sendo um ativador da enzima tiroperoxidase, envolvida na organificação do iodeto. Outro fator que parece ter efeito na inflamação e se relaciona com as DAT, é o glúten. O glúten, um complexo proteico constituído essencialmente por prolaminas e glutelinas, encontra-se naturalmente em cereais como o trigo, o centeio, a cevada e, por contaminação cruzada, na aveia. A digestão incompleta do glúten no trato gastrointestinal resulta na acumulação de péptidos de cadeia longa, causando em certos indivíduos uma resposta inflamatória.
Com este trabalho pretende-se fazer uma revisão narrativa do papel de diversos fatores nutricionais no risco ou na terapia das DAT.
Autoimmune thyroid diseases (AITD) are a group of inflammatory disorders that affect the thyroid gland, characterized by an abnormal immune response against thyroid antigens. The two most common forms of AITD are Hashimoto’s thyroiditis and Graves’ disease. Hashimoto’s thyroiditis is characterized by hypothyroidism due to autoimmune destruction of thyroid tissue and involves the production of autoantibodies against thyroglobulin and thyroid peroxidase. In contrast, Graves’ disease is characterized by hyperthyroidism resulting from excessive stimulation of the thyroid by autoantibodies that bind to TSH receptors on the surface of thyroid follicular cells. Recent studies suggest a link between AITD and certain nutritional and/or dietary factors, which appear to exert an effect on the inflammatory process. Examples include iodine, vitamin D, iron, selenium, and gluten. Iodine, found in foods such as fish, is directly involved in the synthesis of thyroid hormones in the form of the iodide ion and is therefore a crucial element. Both iodine deficiency and excess have negative effects on the thyroid. Vitamin D can be obtained orally, being present in the diet as vitamins D₂ and D₃, or synthesized cutaneously through sunlight exposure, which stimulates the production of vitamin D₃ in the skin. Some studies suggest a link between vitamin D deficiency and the development of immune dysfunction. Selenium is a mineral found in high concentrations in the thyroid, where it plays an important role in cellular redox homeostasis and in the regulation of thyroid hormone synthesis. Iron also appears to play a key role in the production of T₃ and T₄ hormones, acting as an activator of the enzyme thyroid peroxidase, which is involved in the organification of iodide. Another factor that seems to influence inflammation and is associated with AITD is gluten. Gluten is a protein complex composed mainly of prolamins and glutelins, naturally found in cereals such as wheat, rye, barley, and, through cross-contamination, oats. Incomplete digestion of gluten in the gastrointestinal tract can result in the accumulation of long-chain peptides, triggering an inflammatory response in certain individuals. This work aims to provide a narrative review of the role of various nutritional factors in the risk and management of autoimmune thyroid diseases.
Autoimmune thyroid diseases (AITD) are a group of inflammatory disorders that affect the thyroid gland, characterized by an abnormal immune response against thyroid antigens. The two most common forms of AITD are Hashimoto’s thyroiditis and Graves’ disease. Hashimoto’s thyroiditis is characterized by hypothyroidism due to autoimmune destruction of thyroid tissue and involves the production of autoantibodies against thyroglobulin and thyroid peroxidase. In contrast, Graves’ disease is characterized by hyperthyroidism resulting from excessive stimulation of the thyroid by autoantibodies that bind to TSH receptors on the surface of thyroid follicular cells. Recent studies suggest a link between AITD and certain nutritional and/or dietary factors, which appear to exert an effect on the inflammatory process. Examples include iodine, vitamin D, iron, selenium, and gluten. Iodine, found in foods such as fish, is directly involved in the synthesis of thyroid hormones in the form of the iodide ion and is therefore a crucial element. Both iodine deficiency and excess have negative effects on the thyroid. Vitamin D can be obtained orally, being present in the diet as vitamins D₂ and D₃, or synthesized cutaneously through sunlight exposure, which stimulates the production of vitamin D₃ in the skin. Some studies suggest a link between vitamin D deficiency and the development of immune dysfunction. Selenium is a mineral found in high concentrations in the thyroid, where it plays an important role in cellular redox homeostasis and in the regulation of thyroid hormone synthesis. Iron also appears to play a key role in the production of T₃ and T₄ hormones, acting as an activator of the enzyme thyroid peroxidase, which is involved in the organification of iodide. Another factor that seems to influence inflammation and is associated with AITD is gluten. Gluten is a protein complex composed mainly of prolamins and glutelins, naturally found in cereals such as wheat, rye, barley, and, through cross-contamination, oats. Incomplete digestion of gluten in the gastrointestinal tract can result in the accumulation of long-chain peptides, triggering an inflammatory response in certain individuals. This work aims to provide a narrative review of the role of various nutritional factors in the risk and management of autoimmune thyroid diseases.
Descrição
Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas Moniz
Palavras-chave
Doenças autoimunes da tiroide Ferro Iodo Glúten Selénio Vitamina D