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Metabolism > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What is thyroxine derived from?

A

Tyrosine

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2
Q

What type of gland is the thyroid gland?

A

Ductless

Alveolar

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3
Q

How many lobes does the thyroid gland have and how are they connected?

A

2 lobes connected by the isthmus

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4
Q

What is an enlarged thyroid gland called?

A

Goitre

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5
Q

What is the secretory unit of the thyroid gland?

A

Thyroid follicle

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6
Q

What kind of epithelial are found lining the colloid centre?

A

cuboidal or columnar

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7
Q

What protein is found in the colloid?

A

Thyroglobulin (Tg)

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8
Q

Why are the epithelial cells of the thyroid gland polarised?

A

To allow the movement of things through the cells

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9
Q

What does the apical membrane face?

A

The colloid

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10
Q

What does the basolateral membrane face?

A

the extracellular fluid

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11
Q

What do the C cells of the thyroid secrete?

A

Calcitonin

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12
Q

What is the sequence of hormones released to produce thyroid hormone?

A

TRH -> TSH -> T3 + T4

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13
Q

When TSH binds to follicular cells, what does it promote?

A

iodine uptake
production and released of T3 and T4
promotion of gland growth

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14
Q

What are the acute effects of TSH stimulation?

A

synthesis and secretion of T3 and T4

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15
Q

What are the chronic effects of TSH stimulation?

A

growth and division of follicular cells

enlargement of thyroid gland

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16
Q

Which enzyme is required for thyroxine synthesis?

A

Thyroid peroxidase

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17
Q

What kind of molecule is thyroglobulin?

A

large glycoprotein

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18
Q

How is thyroglobulin synthesised?

A

peptide produced is glycosylated at ER
translocated to Golgi
packaged into secretory vesicles
stored as colloid

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19
Q

What are the full names of T3 and T4?

A

tri-iodothyronine

tetra-iodothyronine

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20
Q

Are thyroid hormones fat or water soluble?

A

Fat soluble

21
Q

Where is Tg iodinated?

A

At the apical surface

22
Q

Which of T3 or T4 is more potent?

A

T3 is more potent

23
Q

Which of T3 and T4 has the longer half-life and why?

A

T4 has a longer half-life

has a greater affinity for TBG

24
Q

What is the full name of TBG?

A

Thyronine Binding Globulin

25
Q

What effect does oestrogen have on the thyroid?

A

increased synthesis of TBG

decreased clearance of T3 and T4

26
Q

What happens to T4 in the peripheral tissues?

A

T4 is converted to T3 by deiodination

27
Q

What is the treatment for hypothyroidism?

A

T4

28
Q

How do thyroid hormones increase BMR?

A

increase number and size of mitochondria
increase oxygen consumption and heat generation
increase nutrient utilisation

29
Q

What effects do thyroid hormones have on the nervous system?

A

increase myelination
increase reflex speed
increase mental activity

30
Q

How do the thyroid hormone affect the heart?

A

They increase cardiac output.

31
Q

What are the features of cretinism?

A

mental retardation
coarse features
short stature
delayed sexual development

32
Q

What are the signs of hyperthyroidism?

A 
heat intolerance
increased perspiration
weight loss
tachycardia 
increased appetite
nervousness or tremors
33
Q

Define exopthalmus

A

Bulging of the eyes that can occur as a result of hyperthyroidism

34
Q

What is main cause of hyperthyroidism?

A

Grave’s disease

Autoimmune production of an antibody that stimulates the TSH receptors.

35
Q

What is the treatment for hyperthyroidism?

A

Carbimazole

36
Q

How does carbimazole work?

A

It prevents iodination of the thyroid hormones by inhibiting the enzyme thyroid peroxidase.

37
Q

What are the signs of hypothyroidism?

A 
cold intolerance 
weight gain
bradycardia
constipation
dry skin and brittle nails
poor concentration
38
Q

What is the main cause of hypothyroidism?

A

Hashimoto’s disease

Autoimmune production of antibodies that block the TSH receptors.

39
Q

How does the thyroid develop in an embryo?

A

Develops near the tongue and migrates to the base of the neck.

40
Q

When must a heel prick test be done by?

A

before the baby is 21 days old

41
Q

Where are the T3 receptors?

A

In the nucleus

42
Q

Name some causes of hypothyroidism other than autoimmune

A 
post-surgery 
radioactive iodine
anti-thyroid drugs eg. carbimazole 
lack of TSH production
iodine deficiency
43
Q

Name some causes of hyperthyroidism other than autoimmune

A

excessive T4 therapy
excess iodine
ectopic thyroid tissue

44
Q

What is the term used to describe normal levels of the thyroid hormones?

A

Euthyroid

45
Q

What is a hypopit?

A

When both the TSH and free T4 are low

46
Q

What is the crisis version of hypothyroidism and what are the signs?

A

Myxoedema coma
low temperature
unconscious
barely responsive to pain

47
Q

What is the crisis version of hyperthyroidism and what are the signs?

A

Thyroid storm
very high temperature
high blood pressure
deranged

48
Q

The availability of thyroid hormone is tied to the availability of…

A

iodine

Metabolism (17 decks)

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