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Hormones > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What hormones are produced by the thyroid gland?

A

T3 and T4

Composed of 2 tyrosines linked together w/ e or 4 iodines

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2
Q

What is thyroglobulin?

A

A protein on which thyroid hormones are synthesised
Contains many tyrosines

Thyroid hormones are synthesised by iodisation then coupling

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3
Q

What is thyroid peroxidase?

A

An enzyme involved in synthesis of thyroid hormones

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4
Q

What are the 3 reactions carried out by thyroid peroxidase?

A

Oxidation; iodide to iodine

Addition of iodine to tyrosine acceptor residues on thyroglobulin

Coupling of MIT or DIT

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5
Q

Why is most fo T4 converted to T3?

A

T3 has a higher biological activity

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6
Q

Where is T4 converted to T3?

A

Liver and kidneys

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7
Q

What protein are thyroid hormones bound to in circulation?

A

Thyroxine binding globulin

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8
Q

What hormone stimulates release of thyroid hormones?

A

TSH (from ant pituitary)

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9
Q

What actions are stimulated by TSH?

A 
Iodine uptake 
Iodine oxidation 
Thyroglobulin synthesis 
Thyroglobulin oxidation 
Cell metabolism and growth 
Colloid pinocytosis
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10
Q

What G proteins does TSH act on?

A

Gαs

Gαq

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11
Q

How do thyroid hormones increase BMR?

A

Increase number and size of mitochondria

Stimulate synthesis of enzymes in respiratory chain

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12
Q

What is the effect of thyroid hormones on metabolic pathways?

A

Lipid metabolism;
Stimulate lipolysis and β-oxidation

Carbohydrate metabolism;
Stimulate insulin-dependent entry of glucose
Increase gluconeogenesis and glycogenolysis

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13
Q

What is the sympathomimetic effect of thyroid hormones?

A

Increase adrenoceptor number to increase response to cathecholamines

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14
Q

What is the effect of thyroid hormones on the cardiovascular system?

A

Increase response to catecholamines
Increase CO
Increase peripheral vasodilation => carry body heat to surface

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15
Q

What is the effect of thyroid hormones on the nervous system?

A

Essential for adult function and development

Increase myelination and development of neurones

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16
Q

How do thyroid hormones exert their effects?

A

They function as hormone-activated transcription factors
Modulate gene transcription
Binds to thyroid hormones on DNA => relieves repression of gene transcription => expression of DNA

17
Q

What are some examples of thyroid activated genes?

A

PEPCK
Na/K ATPase
Ca-ATPase

18
Q

What is a goitre?

A

Enlargement of the thyroid gland due to overstimulation

Can accompany hypo- or hyperthyroidism

19
Q

What is hypothyroidism?

A

Low levels of thyroid hormones

20
Q

What are some causes of hypothyroidism?

A 
Failure of thyroid gland 
TSH/TRH deficiency 
Autoimmunity (Hashimoto’s) 
Congenital 
Post surgery (thyroidectomy)
21
Q

What are some symptoms of hypothyroidism?

A 
Fatigue 
Weight gain 
Cold intolerance 
Goitre 
Constipation 
Menorrhagia
22
Q

What is Hashimoto’s?

A

Autoimmune condition against thyroid follicles resulting in hypothyroidism

23
Q

What is hyperthyroidism?

A

Excess thyroid hormones

24
Q

What are some causes of hyperthyroidism?

A 
Autoimmune - Graves’ 
Toxic multinodular goitre 
Thyroid carcinoma 
Drugs eg amiodarone 
Ectopic thyroid tissue
25
Q

What are some Sx of hyperthyroidism?

A 
Weight loss 
Irritability 
Heat intolerance 
Fatigue 
Hyper-reflexive
Breathlessness
Increased bowel movement
26
Q

What is Graves’ disease?

A

Autoimmune condition => hyperthyroidism

Production of thyroid stimulating immunoglobulin (TSI)

Continuous stimulation of thyroid hormone outside of -ve feedback

27
Q

What is the medical treatment of hyperthyroidism?

A

Thionamides - carbimazole, propylthiouracil

Use β-blockers to control Sx until thyroid function is normal

28
Q

What is a side effect of thionamides?

A

Agranulocytosis

Do FBC if pt develops unexplained fever or sore throat, exclude pancytopaenia

29
Q

What is definitive treatment of hyperthyroidism?

A

Radioactive iodine

Thyroidectomy

30
Q

What are some signs of hypothyroidism?

A

Bradycardia
Ataxia
Dry hair and skin
Slow reflexes

31
Q

What is the treatment for hypothyroidism?

A

Levothyroxine

50-100mcg /day
Elderly or ischaemic heart disease - 25mcg

Hormones (7 decks)

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