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Fisiologia do Sistema Endócrino

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Apresentação em tema: "Fisiologia do Sistema Endócrino"— Transcrição da apresentação:

1 Fisiologia do Sistema Endócrino
Terceira parte: A Tireóide    Profa. Adjunto do Depto. Ciências Fisiológicas-CCB-UFSC Como citar este documento: PINTO, Cristina Maria Henrique. Fisiologia Humana: Endocrinofisiologia. Disponível em: <http://www.cristina.prof.ufsc.br>. Acesso em: coloque a data aqui

2 Bibliografia recomendada Livros-textos:
ESQUEMAS PARA FACILITAR O ESTUDO E O ACOMPANHAMENTO DE MINHAS AULAS Bibliografia recomendada Livros-textos: “Fisiologia” Costanzo, 2007, 3ª Ed. (Ed. Elsevier) “Fundamentos de Fisiologia”, Berne et al, 2006, 4ª Ed.(Ed. Elsevier) “Berne & Levy: Fisiologia” Koeppen & Stanton, 2009, 6ª Ed. (Ed. Elsevier) “Fisiologia” Berne et al., 2004, 5ª Ed. (Ed. Elsevier) “Tratado de Fisiologia Médica” Guyton & Hall, 2006, 11ª Ed. (Ed. Elsevier) “Fisiologia” Aires, M. M., 2008, 3ª Ed. (Ed. Guanabara Koogan) “Fisiologia: texto e atlas” Despopoulos e Silbernagl, 2003 (Ed. Artmed)

3 PRESERVE O DIREITO AUTORAL CITANDO A FONTE.
AS FIGURAS AQUI UTILIZADAS FORAM RETIRADAS DE WEBSITES E, QUANDO POSSÍVEL, SÃO SEGUIDAS PELO ENDEREÇO NA INTERNET. PARA CONSULTA A TEXTOS E OUTROS RECURSOS ONLINE, VEJA EM: PRESERVE O DIREITO AUTORAL CITANDO A FONTE.

4 Características da glândula tireóide
This gland is located in the lower part of the neck, below the Adam's apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly - formed by two wings (lobes) and attached by a middle part (isthmus). This is the normal appearance of the thyroid gland on the anterior trachea of the neck. The thyroid gland has a right lobe and a left lobe connected by a narrow isthmus. The normal weight of the thyroid is 10 to 30 grams. It cannot easily be palpated on physical examination. extraído, enquanto disponível, de:

5 Características da glândula tireóide
A practical guide to clinical medicine, UCSD School of Medicine : Willians, 2004

6 HISTOLOGIA DA TIREÓIDE
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7 FOLÍCULOS TIREOIDEANOS E CÉLULAS PARAFOLICULARES (“C”)
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8 Os hormônios foliculares tireoideanos:
Características Síntese Armazenamento Secreção Circulação sistêmica

9 Os Hormônios foliculares tireoideanos
Tiroxina (t4) Triiodotironina (t3) extraído, enquanto disponível, de:

10 Triiodotironina (T3) e Tiroxina (T4)
Os Hormônios foliculares tireoideanos Triiodotironina (T3) e Tiroxina (T4) extraído, enquanto disponível, de:

11 Síntese, armazenamento e secreção dos hormônios tireoideanos
“Human Physiology”, Fox, 2004, 8th ed.

12 Síntese, armazenamento e secreção dos hormônios tireoideanos

13 Fontes dietéticas de Iodo
Table 2-1. Some common sources of iodine in adults USA (1,2) Dietary iodine Daily intake (µg) Dairy products 52 Grains 78 Meat 31 Mixed dishes 26 Vegetables 20 Desserts Eggs 10 Iodized salt 380 Other iodine sources (µg) Vitamin/mineral prep (per tablet) 150 Amiodarone (per tablet) 75,000 Povidone iodine (per mL) 10,000 Ipodate (per capsule) 308,000 extraído, enquanto disponível, de:

14 Circulação e modo de ação dos hormônios foliculares tireoideanos
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15 Efeitos metabólicos dos hormônios foliculares tireoideanos
Overall schema of thyroid hormone effects. The upper portion represents intracellular actions resulting from T3 binding to its nuclear receptor (TR), which is linked to thyroid regulatory elements (TREs) in target DNA molecules. The lower portion catalogs all the various whole body effects of thyroid hormone that sustain increased oxygen consumption and permit disposal of the excess CO2, heat, and metabolic products. Levy et al., 2006

16 Os hormônios foliculares tireoideanos:
Transporte Modo de ação Ações fisiológicas Regulação da secreção

17 Regulação da secreção dos hormônios tireoideanos
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18 Regulação da secreção dos hormônios tireoideanos
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19 Regulação da secreção dos hormônios tireoideanos
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20 Regulação da secreção dos hormônios tireoideanos
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21 Regulação da secreção dos hormônios tireoideanos
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22 Regulação da secreção dos hormônios tireoideanos
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23 Como a deficiência de Iodo na dieta resulta em bócio endêmico
(hipotireoidismo com hipertrofia da tireóide) “Human Physiology”, Fox, 2004, 8th ed.

24 O Bócio endêmico/hipotireoidismo pode ser evitado, incluindo-se pequenas quantidades de Iodo na dieta, por exemplo, no sal de cozinha extraído, enquanto disponível, de: Veja online:

25 A importância dos hormônios tireoideanos no desenvolvimento ósseo

26 HT NA REMODELAGEM ÓSSEA NA VIDA ADULTA
Efeitos indiretos do T3: diferenciação dos osteoclastos por sinalização dos osteoblastos Efeitos diretos do T3: proliferação e diferenciação dos osteoblastos Process of bone remodeling. Signals carried by canalicular and syncytial routes from interior osteocytes, and endocrine signals to resting osteoblasts and lining cells generate local paracrine cytokine signals to nearby osteoclasts and osteoclast precursors. Osteoclasts also recruit their own precursors by paracrine signals. The osteoclasts resorb an area of mineralized bone, and local macrophages complete the clean-up of dissolved elements. The process then reverses to formation as osteoblast precursors are recruited to the site and differentiate into active osteoblasts. These lay down new organic matrix and mineralize it. Thus, new bone replaces the previously resorbed mature bone. Levy et al., 2006

27 HIPOTIREOIDISMO E A FORMAÇÃO ÓSSEA
A, A normal 6-year-old child (left) and a congenitally hypothyroid 17-year-old child (right) from the same village in an area of endemic cretinism. Note especially the short stature, obesity, malformed legs, and dull expression of the mentally retarded hypothyroid child. Other features are a prominent abdomen, a flat broad nose, a hypoplastic mandible, dry scaly skin, delayed puberty, and muscle weakness. Hand x-ray films of a 13-year-old normal child (B) and a 13-year-old hypothyroid child (C). Note that the hypothyroid child has a marked delay in development of the small bones of the hands, in growth centers at either end of the fingers, and in the growth center of the distal end of the radius. Berne et al., 2004

28 Sobre os hormônios tireoideanos
- Estimulam a maioria das funções metabólicas e o consumo de oxigênio. - Uns dos responsáveis pelo crescimento e desenvolvimento corporal e cerebral. Receptores para Horm. Tireoideano na cél-alvo: - Membros dos receptores esteróides. - T3 liga-se mais avidamente ao receptor que T4. - Estimulam a atividade RNA-transcricional. - Aumentam a atividade Na+ - K+ ATPásica. Disfunções de secreção de hormônios da Tireóide Função acima do normal – Hipertireoidismo disfunções orgânicas: do metabolismo basal, da freq. cardíaca e da freq. respiratória; do peso corporal e intolerância ao calor Disfunções psíquicas: ansiedade, paranóia, fobias, labilidade emocional e hipercinesia. Função abaixo do normal – Hipotireoidismo disfunções orgânicas: do metabolismo basal, do peso corporal e intolerância ao frio Deficiência de Hormônios Tireoideanos: - Afeta o desenvolvimento do SNC (cretinismo). - Retarda o crescimento da criança. - Retarda o fechamento das epífises ósseas. - Lentifica a função mental (retardo mental). - Lentifica a mobilização energética. - Pode levar ao coma e morte. Excesso de H. Tireoideanos em adultos: - Aumenta o consumo de oxigênio. - Aumenta a produção de calor. - Aumenta o consumo de reserva energética. - Geralmente causa perda de peso. - Causa perda de cálcio ósseo. - Causa fraqueza muscular esquelética.

29 Alguns exemplos de distúrbios da secreção tireoideana
Cretinismo Congenital Hypothyroid: Congenital hypothyroidism is a relatively common disorder which is screened for at birth. Thyroid hormone is necessary for brain development in the first two years of life. If it is not present in adequate amounts during this period of time, permanent brain damage will occur. As thyroid hormone is necessary for linear growth, severe growth retardation occurs if it is absent during childhood. If treatment is started while the epiphyses are open and undamaged, growth will resume. In addition to the above problems, these patients may have all the other signs and symptoms of hypothyroidism. Congenital Hypothyroid: Typical History                         A 44 yr. old man who has always been cared for by his mother is presented. He is severely retarded and cannot communicate. He is only 40” tall, his epiphyses are still open, although severely damaged. He has very thick, dry skin. His tongue is thick, and he has a saddle nose. He still has his primary teeth; the secondary teeth have not erupted. Veja mais em:

30 Alguns exemplos de distúrbios da secreção tireoideana
cretinismo Myxedematous endemic cretinism in the Democratic Republic of Congo. Four inhabitants aged years : a normal male and three females with severe longstanding hypothyroidism with dwarfism, retarded sexual development, puffy features, dry skin and hair and severe mental retardation. mixedema: edema com acúmulo de mucopolissarídeos/glicosaminoglicanas pois a tiroxina diminui a síntese dos ácidos hialurônico e condroitino- sulfúrico extraído, enquanto disponível, de:

31 Alguns exemplos de distúrbios da secreção tireoideana
Cretinismo Hypothyroidism during fetal development can lead to cretinism. This results as thyroid hormones are responsible for the development of the nervous system. Sufferers have mental impairment and often suffer from dwarfism as their linear growth is affected. The patient in the image below is suffering from cretinism. Male from Ecuador about 40 years old, deaf/mute, unable to stand or walk. Use of the hands was strikingly spared, despite proximal upper-extremity spasticity. From DeLong et al (107).

32 Alguns exemplos de distúrbios da secreção tireoideana
Hipotireoidismo secundário: Deficiência de iodo na dieta (na criança pode provocar o cretinismo) Hipertrofia da tireóide no bócio endêmico Three women of the Himalayas with stage II goiters. extraído, enquanto disponível, de:

33 Alguns exemplos de distúrbios da secreção tireoideana
Primary hypothyroidism occurs when disease of the thyroid gland prevents it from producing adequate amounts of thyroid hormone. Symptoms may vary from mild to severe and from nonspecific to very specific. In general, all metabolic processes slow down. Patients are often fatigued, and may also have depression, decreased intellectual function, and, rarely, overt psychosis (...). Primary Hypothyroid: Typical History 43 y/o patient with the chief complaint of "decreased energy." She complains of fatigue, inability to finish tasks, sleeping more, yet always being tired. She has also noticed a decreased cold tolerance, constipation, and dryness of the skin. She comments that she is always cold, even in the summer. She has a positive family history for thyroid problems, but does not know the details Hipotireoidismo no adulto (exemplo de mixedema)

34 Alguns exemplos de distúrbios da secreção tireoideana
hipertireoidismo Grave's Disease: Grave’s disease is an autoimmune disease in which the immune system produces antibodies which stimulate the TSH receptors of the thyroid gland. The result is the non-suppressible overproduction of thyroid hormone, resulting in the clinical manifestations of hyperthyroidism. Grave’s disease is frequently associatied with exophthalmus and swelling of the periorbital tissues. This infiltrative ophthalmopathy involves an increase in the mass of both retrobulbar connective tissue and extraocular muscles, the latter producing ophthalmoplegias. Patients often complain about dry burning eyes. Rarely there may be skin thickening on the legs referred to as pretibial myxedema. There is often a family history of both Grave’s disease and autoimmune thyroiditis. Grave's Disease: Typical History 23 y/o woman presents with the chief complaint of nervousness. She has a one month history of increased nervousness associated with a short temper, crying easily, and tremor. In addition she states she has lost 25 pounds without dieting, and is always hot. Her eyes protrude and feel dry. extraído, enquanto disponível, de:

35 Alguns exemplos de distúrbios da secreção tireoideana
Hyperthyroidism: Hyperthyroidism is due to an excess amount of free thyroid hormone. There is a generalized increase in metabolic rate, with an increase in oxygen use. The symptoms of hyperthyroidism include heat intolerance, nervousness, increased irritability, palpitations, weight loss with the same or increased food intake, and increased frequency of defecation. Women may have a decreased frequency of menses. Physical findings may include hyperkinesis, warm moist skin, a prominent stare and lid lag. The neurological exam may show a fine tremor and a fast return phase for the deep tendon reflexes(...). Doença de Graves (hipertireoidismo). Jovem mulher com exoftalmia e bócio (Porth, 2004) Hyperthyroidism: Typical History 32 year old man presents with heat intolerance and weight loss. His symptoms started about three months ago and have been getting worse. He has lost ten pounds in the last six weeks but says his appetite is very good. He says he is always hot, even in air-conditioned rooms. After questioning, he also admits to having increased nervousness, trouble concentrating, and palpitations. He is having trouble doing fine motor tasks because of a tremor. Physical exam reveals a patient with warm, smooth, moist skin and a diffuse goiter with a palpable thrill and bruit. Neurological exam showed a fine tremor and fast return phase for deep tendon reflexes.

36 Quer saber mais sobre Fisiopatologia da Tireóide?
Veja em: Thyroid Disease Manager offers an up-to-date analysis of thyrotoxicosis, hypothyroidism, thyroid nodules and cancer, thyroiditis, and all aspects of human thyroid disease and thyroid physiology. It provides physicians, researchers, and trainees (as well as patients) around the world with an authoritative, current, complete, objective, free, and down-loadable source on the thyroid.

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