tiroide, paratiroide e metabolismo do cálcio - ufrgs.br em pdf/38... · disfunções de secreção...

Tiroide, Paratiroide

e Metabolismo do

Cálcio

Tiroide

http://www.pathguy.com/lectures/thyroid.htm#intro

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.

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)

A GLÂNDULA TIREÓIDE


This normal thyroid follicle is lined by a cuboidal follicular epithelium with cells that can add or subtract colloid

depending upon the degree of stimulation from TSH (thyroid stimulating hormone) released by the pituitary

gland. As in all endocrine glands, the interstitium has a rich vascular supply into which hormone is secreted.


A GLÂNDULA TIREOIDE

histologia


A GLÂNDULA TIREOIDE

Os hormônios tireoideanos:

Triiodotironina (T3) e Tiroxina (T4)

http://www.colorado.edu/epob/epob1220lynch/18endo2.html

http://www.colorado.edu/epob/epob1220lynch/18endo2.html

Ações fisiológicas dos hormônios tireoideanos

http://www.gravitywaves.com/chemistry/CHE452/19_Thyroid15.htm

http://www.gravitywaves.com/chemistry/CHE452/19_Thyroid15.htm

Hypothalamic-pituitary-thyroid axis: Thyroid hormone levels are regulated by a feedback inhibition mechanism which

operates along the hypothalamic-pituitary-thyroid axis. The hypothalamus secretes thyrotropin releasing hormone (TRH)

which stimulates the pituitary to secrete thyroid stimulating hormone (TSH). TSH, in turn, stimulates the thyroid gland to

produce and secrete thyroid hormones (T4 and T3) into the circulation. Once levels of T4 and T3 are adequate, further

production of TSH is suppressed according to the familiar negative feedback mechanism. There is, therefore, an inverse

relationship between TSH and thyroid hormone levels. Because physiological activity is exerted by the free hormones

(those not bound to binding proteins), this inverse relationship is actually between TSH and the free thyroid hormones.

http://www.dpcweb.com/medical/thyroid/thyroid_function.html

Regulação da secreção dos hormônios tireoideanos

http://www.dpcweb.com/medical/thyroid/thyroid_function.html

http://www.biol.sc.edu/courses/bio102/thyroid.gif


http://www.biol.sc.edu/courses/bio102/thyroid.gif

http://www.colorado.edu/epob/academics/web_resources/thyroid/thyrost1.gifhttp://www.colorado.edu/epob/academics/web_resources/thyroid/


http://www.colorado.edu/epob/academics/web_resources/thyroid/


animaçãoRegulação da secreção dos hormônios tireoideanos


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

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.

•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.

•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.

Sobre os hormônios tireoideanos

http://www.mscd.edu/~biology/2320course/2320info.htm

PRINCIPAIS FISIOPATOLOGIAS DA TIREOIDE


animação


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

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 (...). Veja mais em:

http://www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html#Hyperthyroidism

Alguns exemplos de distúrbios da secreção tireoideana

http://www.pathguy.com/lectures/thyroid.htm

Hipotireoidismo no adulto

(exemplo de mixedema)



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...

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(...) veja

mais em: http://www.hsc.missouri.edu/~daveg/thyroid/thy_dis.html#Hyperthyroidism


...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.



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.

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.




Metabolismo

do Cálcio

• Vaca leiteira:

• 30 kg de leite = 36

g de Ca2+ = 4 x

[plasmática]

tiroide, paratiroide e metabolismo do cálcio - ufrgs.br em pdf/38... · disfunções de secreção...

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