3: Anatomy and physiology of the thyroid gland Flashcards Preview

Endocrine Week 3 2017/18 > 3: Anatomy and physiology of the thyroid gland > Flashcards

Flashcards in 3: Anatomy and physiology of the thyroid gland Deck (53)
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1
Q

What is the master gland of the endocrine system?

A

Pituitary gland

2
Q

In relation to the thyroid, which hormone is secreted by the hypothalamus and acts on the pituitary gland?

A

TRH

Thyrotrophin releasing hormone

3
Q

Which hormone is secreted by the pituitary gland and acts on the thyroid?

A

TSH

Thyroid stimulating hormone

4
Q

Which hormones are released by the thyroid gland?

A

Thyroxine (T4)

Tri-iodothyronine (T3)

Calcitonin

5
Q

Which glands are found on the posterior aspect of the thyroid?

A

4 parathyroid glands

6
Q

Which nerve could be damaged in thyroid surgery, almost certainly getting you sued?

A

Recurrent laryngeal nerve

Unilateral - swallowing issues

Bilateral - lack of phonation

7
Q

Removal of the parathyroid glands during thyroid surgery may result in ___.

A

hypoparathyroidism

8
Q

Thyroid pathologies have typical appearances on which imaging modality?

A

Ultrasound

9
Q

The thyroid takes up ___. This allows it to be seen on radionucleotide imaging.

A

iodine

10
Q

From wikiped:

Low uptake suggests thyroiditis, high uptake suggests Graves’ disease,[4] and unevenness in uptake suggests the presence of a nodule.

A
11
Q

What carrier protein is found in the follicle of thyroid cells?

A

Thyroglobulin (which carries T3 and T4)

12
Q

What is the fluid area found in the central of a follicle?

A

Colloid

13
Q

Thyroglobulin is found in which part of a thyroid follicle?

A

Colloid

14
Q

What binds to thyroglobulin to produce thyroid hormones?

A

Iodine

15
Q

How are thyroid hormones transported from the colloid to the follicular cells once they have been produced?

A

Pinocytosis

16
Q

How are thyroid hormones transported from the follicular cells into the bloodstream?

A

Exocytosis

17
Q

Where are C cells found?

What do they produce?

A

Parafollicular

Calcitonin

18
Q

Iodine binds to what part of thyroglobulin to form the precursors of thyroid hormones?

A

Tyrosine residue

19
Q

What is the biggest cause of hypothyroidism (i.e lack of thyroid hormone production) globally?

A

Iodine deficiency

20
Q

What antithyroid drugs are used to treat hyperthyroidism?

How do they work?

A

Carbimazole, propylthiouracil

Inhibit iodination of thyroglobulin

21
Q

Why do anti-thyroid drugs have a long onset of action?

A

Prevent NEW thyroid hormones from being made

Still residual thyroid hormone floatin around, and it’s got a half life of around 10 days

22
Q

Which thyroid hormone is

a) most commonly secreted
b) most potent?

A

a) T4

b) T3

23
Q

T4 must be converted to __ before it can work.

A

T3

More potent

24
Q

Where is T4 converted to T3?

A

Liver and kidneys

25
Q

Thyroid hormones are (hydrophilic / hydrophobic).

A

Hydrophobic

26
Q

How are thyroid hormones similar to steroids?

A

Hydrophobic

Pass through cell membrane

Act on nuclear receptors to alter metabolism

Require carrier proteins to travel in blood

27
Q

Thyroid hormones are released from follicular cells in response to which hormone?

A

TSH

28
Q

On which carrier proteins are thyroid hormones transported in the blood?

A

Thyroxine binding globulin (TBG)

Transthyretin

Albuminnnn

29
Q

When thyroid hormones are bound to carrier proteins, they are ___.

A

inactive

30
Q

Free thyroid hormones are (inactive / active).

A

active

31
Q

Where are thyroid hormone receptors found?

A

Everywhere

hence systemic effects

32
Q

How do thyroid hormones work normally?

A

Bind to nuclear receptors to alter gene transcription for genes controlling metabolism, growth, reproduction etc.

33
Q

Thyroid hormones (increase / decrease) the basal metabolic rate.

A

increase basal metabolic rate

34
Q

What process responsible for generating body heat are thyroid hormones responsible for?

A

Thermogenesis

35
Q

What effect do thyroid hormones have on the metabolism of carbohydrates, lipids and protein?

A

Increase the metabolism of all three

36
Q

Which hormone’s secretion itself requires the action of thyroid hormones?

A

Growth hormone

37
Q

The development of which organ is especially dependent on thyroid hormones?

A

Brain

38
Q

How exactly do thyroid problems cause autonomic symptoms?

A

Increase expression of adrenaline receptors

> autonomic symptoms (tachycardia, sweating, anxiety etc.)

39
Q

The related actions of the hypothalamus, pituitary gland, thyroid gland and their hormones are collectively known as what?

A

H-P-T axis

40
Q

The levels of T3 and T4 affect the secretion of TRH and TSH. What is this an example of?

A

Negative feedback

41
Q

TSH receptors, found on thyroid ___ cells, are examples of which type of receptor?

A

follicular cells

G protein coupled receptors

42
Q

G protein receptor function involves the conversion of ATP to ___, which causes an effect in the cell.

A

cAMP

43
Q

Measuring thyroid hormones in sick patients is not advised - why?

A

Non-thyroid illness

STRESS increases the secretion of thyroid hormones which can be misinterpreted

44
Q

Stress (increases / inhibits) thyroid hormone secretion.

A

inhibits secretion

45
Q

What external factors influence the secretion of thyroid hormones?

A

Temperature

Circadian rhythm

46
Q

Which family of enzymes deactivate thyroid hormones?

A

Deiodinase enzymes

47
Q

Different types of deiodinase enzymes are found in (the same / different) tissues of the body.

A

different tissues, different enzymes

48
Q

Which deiodinase enzyme converts T4 to T3 in liver and kidney cells?

A

D2

49
Q

Where are thyroid hormone receptors found in a cell?

A

Within the nucleus

50
Q

Different __ __ receptors are found in different parts of the body.

A

thyroid hormone

51
Q

What, related to thyroid hormone receptors, can produce signs and symptoms of hyper and hypothyroidism?

A

Gene mutations

Producing RESISTANCE TO THYROID HORMONES

52
Q

What is the appearance of hypothyroidism called in

a) adults
b) babies?

A

Myxoedema

Cretinism

a bit old-fashioned now

53
Q

What is thyroid stimulating immunoglobulin an important part of?

A

Graves disease

behaves like TSH but isn’t regulated by negative feedback, so it produces hyperthyroidism