Transcript Sobre os Hormônios Tireoideanos

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
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)
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PRESERVE O DIREITO AUTORAL CITANDO A FONTE.
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: http://www.pathguy.com/lectures/thyroid.htm#intro
Características da glândula tireóide
http://www.healthopedia.com/pictures/site-of-thyroid-scan.html
A practical guide to clinical medicine, UCSD School of Medicine :
http://medicine.ucsd.edu/clinicalmed/head.htm
Willians, 2004
HISTOLOGIA DA
TIREÓIDE
extraído, enquanto disponível, de:
http://www.biosbcc.net/barron/physiology/endo/thyr.htm
http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/Endoc
rine_System/Endocrine_Histology.htm
FOLÍCULOS TIREOIDEANOS E CÉLULAS
PARAFOLICULARES (“C”)
extraído, enquanto disponível, de: http://education.vetmed.vt.edu/Curriculum/VM8054/Hp/LECLIST.HTM
Os hormônios foliculares
tireoideanos:
 Características
 Síntese
 Armazenamento
 Secreção
 Circulação sistêmica
Os Hormônios foliculares tireoideanos
Tiroxina (t4)
Triiodotironina (t3)
extraído, enquanto disponível, de: http://smid.blueprint.org/smidblast_browse.php?gi=586092
Os Hormônios foliculares tireoideanos
Triiodotironina (T3) e Tiroxina (T4)
extraído, enquanto disponível, de:
http://www.colorado.edu/epob/epob1220lynch/18endo2.html
Síntese, armazenamento e secreção dos hormônios tireoideanos
“Human Physiology”, Fox, 2004, 8th ed.
Síntese, armazenamento e secreção dos hormônios tireoideanos
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
20
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: http://www.thyroidmanager.org/Chapter15/15-frame.htm
Circulação e modo de ação dos hormônios foliculares tireoideanos
extraído, enquanto disponível, de: http://www.biosbcc.net/barron/physiology/endo/thyr.htm
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
Os hormônios foliculares
tireoideanos:
 Transporte
 Modo de ação
 Ações fisiológicas
 Regulação da secreção
Regulação da
secreção dos
hormônios
tireoideanos
extraído, enquanto disponível, de: http://connection.lww.com/products/braun-carie/PreviewChapters.asp
Regulação da secreção dos hormônios tireoideanos
extraído, enquanto disponível, de: http://www.colorado.edu/eeb/web_resources/thyroid/ Veja online: http://biologyinmotion.com/thyroid/
Regulação da secreção dos hormônios tireoideanos
extraído, enquanto disponível, de: http://www.colorado.edu/eeb/web_resources/thyroid/ Veja online: http://biologyinmotion.com/thyroid/
Regulação da secreção dos hormônios tireoideanos
extraído, enquanto disponível, de: http://www.biosbcc.net/barron/physiology/endo/thyr.htm
Regulação da secreção dos hormônios tireoideanos
extraído, enquanto disponível, de: http://www.biosbcc.net/barron/physiology/endo/thyr.htm
Regulação da secreção dos hormônios tireoideanos
extraído, enquanto disponível, de: http://www.colorado.edu/eeb/web_resources/thyroid/ Veja online: http://biologyinmotion.com/thyroid/
http://www.colorado.edu/epob/academics/web_resources/thyroid/thyrost1.gif
Como a deficiência de Iodo na
dieta resulta em bócio
endêmico
(hipotireoidismo com
hipertrofia da tireóide)
“Human Physiology”, Fox, 2004, 8th ed.
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: http://www.colorado.edu/eeb/web_resources/thyroid/ Veja online: http://biologyinmotion.com/thyroid/
http://www.colorado.edu/epob/academics/web_resources/thyroid/thyrost1.gif
A importância dos
hormônios tireoideanos
no desenvolvimento
ósseo
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
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
Sobre os hormônios tireoideanos
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 célalvo:
- Membros dos receptores esteróides.
- T3 liga-se mais avidamente ao receptor que
T4.
- Estimulam a atividade RNA-transcricional.
- Aumentam a atividade Na+ - K+ ATPásica.
 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.
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.
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: http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/thyroid_preg.html
Alguns exemplos de distúrbios da secreção tireoideana
cretinismo
Myxedematous endemic cretinism in the Democratic Republic of Congo. Four inhabitants aged 15-20 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: http://www.thyroidmanager.org/Chapter20/20-frame.htm
http://members.tripod.com/~Histology_2/conj_ic.htm
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.
http://cal.man.ac.uk/student_projects/2002/MNBY9APB/THETHYrOIDCLINICAL.htm
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).
http://www.thyroidmanager.org/Chapter20/20-frame.htm
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: http://www.thyroidmanager.org/Chapter20/20-frame.htm
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)
http://www.pathguy.com/lectures/thyroid.htm
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: http://www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html#Hyperthyroidism
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(...).
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
Doença de Graves (hipertireoidismo).
Jovem mulher com exoftalmia e bócio
(Porth, 2004)
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.
http://www.pathguy.com/lectures/thyroid.htm
Quer saber mais sobre
Fisiopatologia da Tireóide?
Veja em:
http://www.thyroidmanager.org
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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