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BRS1 - Valentine > THYROID glands > Flashcards

THYROID glands Flashcards

(44 cards)

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1
Q

What is the middle lobe of the thyroid in which not everyone has?

A

Pyramid- connected to the isthmus

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2
Q

What are the types of cells and molecules in thyroid gland?

A

Follicular cells and colloid (makes follicles) Parafollicular cells

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3
Q

What is the function of parafollicular cell?

A

Makes calcitonin

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4
Q

What is the function of follicles

A

Makes thyroxine

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5
Q

How many parathyroid glands do we have ; name them

A

4 Superior and inferior on BOTH LOBES

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6
Q

What is the function of the parathyroid gland?

A

Calcium metabolism; to control calcium levels

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7
Q

What nerve lies very close to the thyroid? What does it supply?

A

Recurrent laryngeal nerve Supplies vocal cords

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8
Q

Describe the embryology of thyroid gland: how it forms in embryo

A

Midline outpouching from floor of pharynx; originates from base of tongue

Thryoglossal ducts develops

Divides into 2 lobes

Thyroglossal duct disappear leaving FORAMEN CAECUM

Final position by week 7 Thyroid gland develops

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9
Q

In the steps of synthesis of thyroxine, describe what happens in the FOLLICULAR CELLS

A

Iodide ions diffuse into follicular cell from capillary TSH bind to TSH-R;

This stimulates production of TG (thyroglobulin)

Also TPO is made(Thyroperoxidase)

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10
Q

In the steps of synthesis of thyroxine, describe what happens in the COLLOID

A

Iodide ions diffuse into colloid and becomes OXIDISED

TG goes into colloid and bind with Iodine (iodination).

MIT and DIT are formed

They undergo coupling reactions with DIT to form T3 and T4

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11
Q

Describe the roles of TPO, in synthesis of thyroxine

A

Binds to H2O2 and Catalyses TG reactions

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12
Q

What properties of thyroglobulin allows it to undergo iodination

A

It has tyrosine residue that can be iodinated

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13
Q

What happens to T3 and T4 after they have been synthesised

A

Secreted out of thyroid into the blood to target organ

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14
Q

What’s the acronym of the following MIT,DIT, T3 and T4

A

MIT- Monoiodotyrosine DIT- diiodotyrosine T3- 3,5,3 TRI-iodothyronine T4- thyroxine

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15
Q

Of the following which is active and inert T3, T4

A

T3- active T4- inert

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16
Q

What compounds can T4 be deiodinated to? Which is active

A

T3 ( 2 iodine in primary bottom chain )

Reverse T3- 2 iodine in top secondary chain; this is INACTIVE

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17
Q

What enzymes convert T4 to T3; where are they found?

A

Deiodinase enzymes; found in all target cells.

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18
Q

Outline the origins of the main T3 in target cells

Study These Flashcards
A

80% from T4

20% from direct thyroidal secretion

19
Q

What proteins does T3/T4 bind to in order to be transported in the blood.

Study These Flashcards
A

TBG(Thyroid binding globulin)- 70-80%

Albumin- 10-15%

Prealbumin-

20
Q

What percentage of T3 and T4 are unbounded to proteins in the blood; what are their properties?

Study These Flashcards
A
  1. 05% of T4
  2. 5% of T3

They are bio active

21
Q

What does T3 and T4 do in target cells in order to bring about a physiological effect

Study These Flashcards
A

Alter gene expression in nucleus

22
Q

What is the function of thyroid in foetus

Study These Flashcards
A

Growth and development; especially the CNS

23
Q

How does the baby gets its thyroid?

Study These Flashcards
A

From mother; it crosses placenta

24
Q

What is untreated congenital hypothyroidism called?

25
How is TSH measured in infant? What is the result if baby doesn’t make its own thyroxine
Heel-prick test after day 5 High TSH readings if baby cant make its own thyroxine
26
What is the half-lives of T3 and T4 respectively?
T3- 2 days T4- 7-9 days
27
Describe how thyroid hormone production is controlled?
TRH- TSH makes T3 AND T4 T3 and T4 trigger negative feedback to reduced TRH production both at hypothalamus and pituitary gland Somatostatin reduce TSH production Iodide reduce thyroxine production (Wolff-Chalkoff effect)
28
Are thyroid disorders more common in males or females
Women (4:1)- due to autoimmmunity
29
Which is more common?; hyperthyroidism or hypothyroidism
They’re both common (same prevalence)
30
In hypothyroidism, what happens when there’s autoimmune damage to the thyroid? In blood?
Thyroxine levels decline TSH levels increase
31
What is the name of the commonest form of hypothyroidism
Hashimoto’s thyroiditis Presence of one autoimmune disease increases risk of others
32
What are the signs and symptoms of primary hypothyroidism
* Deepening voice * Depression and tiredness * Cold intolerance * Weight gain and reduced appetite * Constipation * Bradycardia * Eventual myxoedema coma
33
What is the mechanism of Levothyroxine
Same molecule as T4; undergo same processes
34
How is dosing of levothyroxine measured and given?
Adjusted to TSH level; given until TSH levels is normal; administered ORALLY
35
What are the indications of giving levothyroxine?
Hypothyroidism Hyperthyroidism- after treatment to stop production of T4; radioactive iodine
36
What are potential complications of levothyroxine
Weight loss Headaches Heart attack(arrhythmia); only if TOO MUCH thyroxine is administered
37
What are the consequences of using combination of T4 AND T3
Toxic; palpitation, tremor, anxiety Suppresses TSH
38
What happens when there’s hyperthyroidism
Thyroxine levels rise up TSH levels drop
39
What are the potential causes of hyperthyroidism
Graves diseases Toxic multinodular goitre Solitary toxic nodule
40
What are the 3 signs of Graves’ disease and explain why?
Smooth goitre - autoantibody bind to stimulate TSH-R in thyroid Exophthalmos- antibodies bind muscle BEHIND the eye Pretibial myxoedema- antibodies stimulate growth of soft tissues of shins
41
What are the signs and symptoms of Hyperthyroidism
* Heat intolerance * Myopathy * Mood swings * Diarrhoea * Hand tremors * Weight loss even when appetite goes up * Palpitation * Sore eyes, goitre
42
What connects the two lobes of thyroid?
Isthmus
43
What is the function of Thyroid hormone in the body?
Increase BMR Potentiate actions of catecholamines (tachycardia and lipolysis) Effects on GI,CNS and reproductive systems Increase protein, carbohydrate and fat metabolism Bone maturation and growth formation Increase protein synthesis, glycogenolysis and gluconeogenesis
44
Draw the whole image of thyroid secretion what is needed to activate TPO? And what reactions does it catalyses
H2O2 Iodination and coupling reactions

BRS1 - Valentine (54 decks)

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