Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Endocrine System > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

At what gestational age does the thyroid gland first appear?

A

3-4 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where in the foetus does the thyroid gland first appear?

A

At the base of the tongue where the foramen caecum will exist

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The thyroid descends as the thyroglossal duct via the hyoid bone and the proximal part regresses by which point in gestation?

A

5-7 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

From where do the parafollicular cells appear in the foetus?

A

4th and 5th branchial pouches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Sometimes, an additional lobe is present in the thyroid. What is the name of this lobe?

A

Pyramidal lobe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the name of the part of the thyroid which connects the right and left lobes?

A

Isthmus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the name of the extracellular substance which exists in the lumen of the follicles of the thyroid gland?

A

Colloid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where in the thyroid gland do C cells exist?

A

Interspersed between follicular cells in the follicles and also in spaces between the follicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the arrangement of the follicular cells of the thyroid?

A

These are arranged in a single layer of cells to form a spheroidal follicle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is produced by the parafollicular cells of the thyroid gland?

A

Calcitonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is produced by the follicular cells of the thyroid gland?

A

Triiodothyronine (T3)

Thyroxine / Tetraiodothyronine (T4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The majority of T3 and T4 are bound to what protein in the blood?

A

Thyroxine binding globulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What type of hypothyroidism is caused by Sheehan’s syndrome?

A

Secondary hypothyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the name for the dwarfism and severe mental retardation cause by hypothyroidism in infancy?

A

Cretinism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In adults, what are the clinical features of hypothyroidism?

A 
Myxoedema
slowed physical and mental activity
fatigue
cold intolerance
periorbital oedema
coarsening of skin and facial features
cardiomegaly
effusions
hair loss
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What antibodies are involved in Hashimoto’s thyroiditis?

A

Anti-TSH receptor antibodies
anti-thyroglobulin antibodies
Antithyroid peroxidase antibodies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Hashimoto’s thyroiditis is usually a diffuse process. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

You would expect to see a goitre in Hashimoto’s thyroiditis. T/F?

A

True - although a person could still have the condition even if a goitre was not present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What pathohistological changes in the thyroid would you expect to see with Hashimoto’s thyroiditis?

A

Paler
resembling a lymph node on section - lymphocytes, plasma cells, macrophages and germinal centre formation
oncocytic change in the epithelium (Hurthle cells)
fibrosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What percentage of men and women are affected by thyroid disorders?

A

5% of women

0.5% of men

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the approximate weight of the thyroid glands?

A

10-20g

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When stimulated, what shape are the follicular cells of the thyroid gland and what affect does stimulation have on the colloid?

A

Columnar cells and the lumen is depleted of colloid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

When the thyroid gland is stimulated, what shape are the follicular cells and what affect does this have on the colloid?

A

Flat cells

Colloid accumulates in the lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Iodine is necessary for thyroid hormone synthesis. Iodine is obtained in the diet from…?

A

Seawater
Fruit
Vegetables

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How much iodine is required in the diet each day?

A

150-300micrograms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What public health measure has reduced iodine deficiency?

A

Iodine supplementation of salt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Oral iodine is reduced to iodide in the GI tract before absorption. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Iodide ions are actively transported into the follicular cells of the thyroid by co-transport with which electrolyte?

A

Sodium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the name of the transport protein which carried iodide into vesicles on the apical membrane of follicular cells in the thyroid?

A

Pendrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Which enzymes catalyses the oxidation of iodide to iodine and the binding of this iodine to tyrosine residues on thyroglobulin?

A

Thyroid peroxidase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Once T3 and T4 has been produced, what happens to the thyroglobulin?

A

It is hydrolysed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Where in the cell are T3 and T4 cleaved from thyroglobulin?

A

Lysosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

The combination of iodine and tyrosine forms…?

A

mono iodinated thyronine (MIT) and di iodinated thyronine (DIT)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

T3 is released in greater quantities from the thyroid gland than T4. T/F?

A

False- the opposite is true

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

T4 can be converted to T3 in the periphery by the process of…?

A

5’ deionisation of T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

T3 is more potent than T4. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

99.5% of circulating thyroid hormones are protein bound. To what proteins are they bound?

A

Globulin
Transthyretin
Albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

The free component of circulating thyroid hormone is the active and regulated component. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Where in the cell do the receptors for thyroid hormones exist?

A

In the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Almost all tissues have nuclear receptors for T3. T/F?

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

In primary hypothyroidism there is low T4 but high TSH. How is this different in secondary hypothyroidism?

A

In secondary hyperthyroidism there is both low TSH and T4

42
Q

What factors may cause hyperthyroidism?

A

Autoimmune reactions such as Graves’ disease
Toxic adenoma
Multinodular goitre
Thyroiditis

43
Q

Excess administration of thyroxine will cause an excess of thyroid hormone. Why is this not classed as hyperthyroidism?

A

This is thyrotoxicosis - an increase in the level of thyroid hormone. Hyperthyroidism comes under the umbrella of thyrotoxicosis but specifically refers to increased thyroid hormone levels due to overactivity of the thyroid gland.

44
Q

What are the clinical features of hyperthyroidism?

A 
Weight loss
Tremor
heat intolerance
diarrhoea
tachycardia
hypertension
palpations
sweating
45
Q

What percentage of patients with Graves’ disease will develop dermopathy?

A

1-2%

46
Q

What eye problems may occur in Graves’ disease?

A 
Lid lag
periorbital oedema
proptosis
diplopia
Nerve compression
erythema
conjunctivitis
47
Q

What are the features of dermopathy as seen in Graves’ disease?

A

Soft tissue swelling

Clubbing of the finger

48
Q

What are the treatment options for hyperthyroidism?

A

Antithyroid drugs
Surgery
Radio iodine

49
Q

What is the rare and severe side effect of the use of carbimazole and Propylthiouracil?

A

Agranulocytosis

50
Q

Conception should be delayed for at least how may months after receiving radio iodine therapy?

A

4 months

51
Q

Radio iodine therapy may worsen eye disease in people with Graves’ disease. T/F?

A

True

52
Q

What is the most common side effect of radio iodine therapy?

A

Hypothyroidism

53
Q

What complications may result from thyroidectomy?

A 
Haemorrhage
recurrent laryngeal palsy
permanent hypocalcaemia
hypothyroidism
hypoparathyroidism
infection
keloid formation
54
Q

Hashimoto’s disease is more common in men than in women. T/F?

A

False the opposite is true

55
Q

Other than hashimotot;s thyroiditis, what factors could cause hypothyroidism?

A 
Thyroidectomy
Thyroiditis (often viral)
Drug induced
Pituitary disease
Severe iodine deficiency
56
Q

What are the symptoms of hypothyroidism?

A 
weight gain
depression
thin hair
anaemia
lethargy
constipation
cold intolerance
poor concentration
hoarseness
menorrhagia
bradycardia
dry skin
slow relaxing reflexes
57
Q

What does of levothyroxine is usually given to patients with hypothyroidism?

A

1.7-2.0 mg/kg/day

58
Q

In what patients is levothyroxine started on lower doses?

A

Elderly patients

Patients with CV disease

59
Q

What other medications may interfere with levothyroxine?

A

Proton pump inhibitors
Ferrous sulphate
Calcium

60
Q

What is the normal TSH range?

A

0.5-5mU/L

61
Q

Atrial fibrillation and osteoporosis are possible side effects of levothyroxine. T/F?

A

True

62
Q

Thyroid cancer can be differentiated or undifferentiated. Which has the better prognosis?

A

Differentiated

63
Q

Papillary cancer comprises what percentage of cases of differentiated thyroid cancer?

A

17%

64
Q

Follicular cancer comprises what percentage of cases of differentiated thyroid cancer?

A

13-20%

65
Q

Medullary carcinoma of the thyroid comprises what percentage of cases of differentiated thyroid cancer?

A

6%

66
Q

Mixed differentiated thyroid cancer comprises what percentage of cases of differentiated thyroid cancer?

A

50%

67
Q

The isthmus of the thyroid lies on top of which tracheal cartilages?

A

2nd - 4th tracheal cartilages

68
Q

Some people also have a pyramidal lobe of the thyroid. What embryological structure is this a remnant of?

A

Thyroglossal duct

69
Q

When the larynx rises during swallowing, the thyroid gland rises with it. Why does this happen?

A

The connective tissue capsule of the thyroid adheres to the larynx

70
Q

Which nerve lies behind the thyroid and thus can become damaged in thyroid surgery causing hoarseness and impaired function of the voice?

A

Recurrent laryngeal nerve

71
Q

The thyroid receives blood supply from the superior and inferior thyroid arteries. Where do these arise from?

A

Superior thyroid artery arises from the external carotid

Inferior thyroid artery arises from the subclavian artery

72
Q

The thyroid is drained by the superior, middle and inferior veins. Where do each of these veins drain to?

A

Superior and middle thyroid veins drain to the internal jugular vein
Inferior thyroid vein drains to the brachiocephalic vein

73
Q

To what nodes do the lymph vessels of the thyroid drain to?

A

Deep cervical nodes

74
Q

Which vein are the deep cervical nodes associated with?

A

Internal jugular vein

75
Q

Other than iodide, what electrolyte does pendrin transport?

A

Chloride

76
Q

Thyroglobulin is synthesised by the follicular cells. How does it reach the colloid?

A

By exocytosis

77
Q

T3 and T4 must be cleaved from thyroglobulin before secretion into the blood - this occurs inside the cell. How is the T3/4 containing thyroglobulin moved from the colloid back into the follicular cell?

A

By endocytosis

78
Q

Other than stimulating T3/4 production, what effects does TSH have on the thyroid?

A

It increases DNA replication, cell devision and increases the amount of rough ER and other cellular machinery required by the follicular cells for protein synthesis. I.e. TSH induces hypertrophy of the follicular cells

79
Q

What effect do thyroid hormones have on metabolism?

A

Increase metabolic rate
Increase carbohydrate absorption in small intestine
Increase gluconeogenesis
Increase fatty acid release from adipocytes
Increases action of Na/K-ATPases

80
Q

Thyroid hormones increases sympathetic nervous system activity. How do they accomplish this?

A

Up regulate beta adrenergic receptors in many tissues

81
Q

T3 is required for the normal production of which hormone from the anterior pituitary gland?

A

Growth hormone

82
Q

T3 is important in the development of which body system?

A

Nervous system - involved in the formation of action potentials, the production of synapses and the growth of dendrites

83
Q

T3 is important for normal nerve and muscle reflexes and cognition. T/F?

A

True

84
Q

What is the most common cause of hypothyroidism in Western countries?

A

Hashimoto’s (autoimmune) thyroiditis)

85
Q

What antibodies may be present in Hashimoto’s thyroiditis?

A

Anti-thyroglobulin
Anti-thyroid peroxidase
Inhibitory TSH receptor binding antibodies

86
Q

Other than iodine deficiency or autoimmune conditions, what else can result in hypothyroidism?

A 
Thyroidectomy
Radio iodine therapy
Radiotherapy
Toxic exposure to certain drugs
Infiltrative diseases
87
Q

Explain how non-pitting oedema may occur in patients with hypothyroidism?

A

In severe, untreated hypothyroidism, glycasoaminoglycans can accumulate in the interstitial space (T3 normally acts to prevent over expression of these) and water becomes trapped within these molecules. This causes a characteristic non-pitting oedema

88
Q

Cretinism is reversible if thyroid replacement therapy is started rapidly. t/f?

A

True - if not started soon enough then it is not reversible

89
Q

What dose of levothyroxine is usually given to patients?

A

1.7-2.0 mg/kg/day

90
Q

The main complication of treatment of hypothyroidism with levothyroxine is over-replacement. This increases the risk of what conditions?

A

Osteoporosis

Atrial fibrillation

91
Q

What is the most common cause of hyperthyroidism?

A

Graves’ disease

92
Q

What class of antibody is present in Graves’ disease?

A

IgG

93
Q

What is the name for the antibody which is present in Graves’ disease and what is its action?

A

Long acting thyroid stimulator (LATS). This is analogous to normal TSH and binds to the TSH receptor on follicular cells to cause an increase in production of T3/4 by the thyroid which is not subject to normal negative feedback inhibition

94
Q

What clinical features of Graves’ disease may be present in the eyes?

A 
Lid lag
erythema
conjunctivitis
proptosis
periobital oedema
diplopia
nerve compression
95
Q

What are the signs of dermopathy which can occur in Graves’ disease?

A

Soft tissue swelling

Clubbing of the fingers

96
Q

Other than Graves’, what conditions can cause hyperthyroidism?

A

Toxic adenoma
Multinodular goitre
thyroiditis

97
Q

What medications are used to control the cardiovascular symptoms of hyperthyroidism?

A

Beta blockers or calcium channel blockers

98
Q

What are the possible side effects of antithyroid drugs?

A

Skin rash

Very rarely agranulocytosis can occur

99
Q

What is a goitre?

A

An enlarged thyroid gland

100
Q

Why might a goitre be present in primary hypothyroidism?

A

Thyroid gland failure or iodine deficiency causes a decrease in circulating levels of thyroid hormone meaning there is little negative feedback on the anterior pituitary and hypothalamus meaning that TSH levels are high. TSH levels normally stimulate thyroid hormone production and hypertrophy and hyperplasia of the follicular cells. TSH cannot in this case work to produce more thyroid hormone but still exhibits its other functions resulting in enlargement of the thyroid even though the gland is still underproducing

101
Q

Why might goitre be present in hyperthyroidism?

A

Excessive secretion of TSH from hypothalamic or anterior pituitary defects results in overstimulation of thyroid growth and secretion
In Graves; the goitre occurs because LATS (the Graves’ antibody) also stimulates thyroid gland growth as well as enhancing secretion of thyroid hormone

102
Q

Hyperthyroidism does not always result in goitre formation. In what causes of hyperthyroidism would you least expect to find a goitre?

A

Any cause of hyperthyroidism resulting from overactivity of the thyroid in the absence of overstimulation such as an uncontrolled thyroid tumour

Endocrine System (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions