Thyroid: Science and Diseases Flashcards Preview

Y2 Endocrine > Thyroid: Science and Diseases > Flashcards

Flashcards in Thyroid: Science and Diseases Deck (131):
1

Where do the thyroid lobes attach?

thyroid and cricoid cartilages

2

Which cartilages does the thyroid attach? Which is superior and which is inferior?

Thyroid (superior), Cricoid (inferior)

3

Where does the isthmus of the thyroid gland lie?

2-3rd tracheal cartilages -- C5-T1 vertebrae

4

Where does the thyroid gland originally develop?

between the anterior and posterior parts of the tongue, where the foramen caecum is found in adults

5

How does the thyroid migrate to its adult location?

via the thyroglossal duct - around week 7

6

Working anteriorly to posteriorly, what is the first level of fascia found at the neck?

Superficial fascia

7

What does the superficial fascia of the neck contain?

platysmus

8

Working anteriorly to posteriorly, what is found after the superficial fascia in the neck?

anterior investing fascia

9

What does the anterior investing fascia contain?

the sternocleidomastoid muscles

10

Working anteriorly to posteriorly, what is found after the anterior investing fascia in the neck?

pretracheal fascia

11

What is found within the pretracheal fascia? (5)

strap muscles, trachea, oesophagus, recurrent laryngeal nerves, thyroid gland

12

What is found bilaterally to the pretracheal fascia in the neck?

carotid sheath

13

What is found within the carotid sheath? (4)

internal jugular vein, deep cervical lymph nodes, vagus nerves, carotid arteries

14

Which fascia is found beyond the pre-tracheal fascia?

pre-vertebral fascia

15

What is found within the pre-vertebral fascia?

c-vertebrae, postural neck muscles

16

What muscle is found within the posterior investing fascia?

the trapezius muscles (bilaterally)

17

Which arteries supply the thyroid gland? (2)

superior and inferior thyroid arteries

18

What are the origins of the superior and inferior thyroid arteries?

superior - external carotid; inferior - branch of subclavian

19

Which veins does the thyroid gland drain? (3)

the superior (2), middle (2) and inferior thyroid (1) veins

20

Where do the veins from the thyroid gland drain?

superior and middle --> internal jugular --> brachiocephalic; inferior --> brachiocephalic

21

Which lymph nodes does the thyroid gland drain into? (4)

the inferior pretracheal node; paratrachial nodes; superior deep cervical nodes and deep cervical nodes

22

Which aortic arch is the subclavian artery formed from?

4th

23

Which aortic arch is the arch of the aorta formed from?

4th

24

Name the 4 strap muscles

Omohyoid, sternohyoid, sternothyroid, thyrohyoid

25

What 3 things does the thyroid gland secrete?

T4 (thyroxine), T3 (triiodothyronine), calcitonin

26

What naturally causes an increase in the size of the thyroid gland?

menstruation and pregnancy

27

Innervation of the thyroid gland (2)

ANS including Vagus nerve (Parasympathetic) and the sympathetic trunk

28

Describe the structure of the thyroid gland

follicles surround by follicular cells; parafollicular C cells found dotted about

29

What is found within the follicle of the thyroid gland?

colloid - tyrosine containing thyroglobulin

30

How are T3/T4 secreted into the blood stream?

via pinocytosis

31

How is T3 made?

Iodine taken into the follicle is attached to tyrosine residues in the form of mono-iodotyrosine (MIT) or di-iodotyrosine (DIT). T3 is made up of MIT+DIT

32

How is T4 made?

Iodine taken into the follicle is attached to tyrosine residues in the form of mono-iodotyrosine (MIT) or di-iodotyrosine (DIT). T4 is made up of DIT + DIT

33

Which thyroid hormone is more potent?

T3

34

Which thyroid hormone is more biologically active?

T3

35

Which thyroid hormone is most commonly secreted?

T4

36

Where is T4 converted to T3?

the liver and kidney

37

What stimulates the release of T3 and T4 from the follicular cell?

TSH

38

How are T3/T4 carried within the blood stream and why?

T3/T4 are hydrophobic so are carried in the plasma bound to plasma proteins - when they are in the free form they are biologically active

39

Name the 3 proteins which T3/T4 are most commonly bound to

Thyroxine binding globulin (TBG) ~70%; Transthyretin thyroxine binding pre-albumin (TTR); Albumin (5%)

40

Which form of T3/T4 is more closely correlated to the metabolic state?

free T3 and free T4

41

What is the result of increasing TBG?

increased total T4, not free T4

42

States where there may be increased TBG (4/7)

pregnancy, newborn, hepatitis, biliary cirrohosis, oral contraceptive pill (or other sources of oestrogen), acute intermittent porphyrias, heroin

43

What is the result of decreasing TBG?

decreased total T4, not free T4

44

States where there may be a decrease in TBG (4/7)

androgens, large doses of glucocorticoids, active acromegaly, severe systemic illness, chronic liver disease, phenytoin, carbemazepine

45

Physiological effect of increasing thyroid hormones (5/8)

increased BMR; increased thermogenesis; increased carbohydrate/lipid metabolism; increased protein synthesis; growth; development of foetal/neonatal brain; normal CNS activity

46

How does thyroid hormone affect the response to adrenaline?

increases responsiveness to adrenaline and NA by increasing the number of receptors --> increase in HR and force

47

Why is propanolol an initial treatment of hyperthyroidism?

It antagonises the adrenoreceptors to reduce HR and force which can be found in hyperthyroidism

48

How does thyroid hormone increase BMR?

increases the number and size of mitochondria, increases oxygen use and ATP hyrdolysis and increases the synthesis of respiratory chain enzymes

49

How much of temperature regulation is affected by thyroid hormone?

30%

50

How does thyroid hormone affect carbohydrate metabolism?

increased blood glucose through glycogenolysis and gluconeogenesis while increasing insulin dependent uptake into cells

51

How does thyroid hormone affect growth?

GHRH production and secretion requires TH

52

How does thyroid hormone affec the development of the neonatal brain?

increases myelinogenesis and axonal growth

53

How is thyroid hormone release regulated?

Thyrotropin RH is released from the hypothalamus and stimulates TSH release from the anterior pituitary

54

How do T3/T4 impact the release of TRH?

negative feedback system: T3/T4 inhibit the release of TRH and TSH

55

What kind of receptor is the TSH receptor?

A GPCR which stimulates cAMP in the follicular cell

56

When is TH highest in the day?

Late at night; lowest in the morning

57

How many types of de-iodinase enzymes are there?

3

58

Which de-iodinase enzyme is most important for converting T4 to T3 ?

type 2

59

Where is type 2 de-iodinase enzyme mostly found?

within the heart, skeletal muscle, CNS, fat, thyroid and pituitary

60

Where is type 3 de-iodinase enzyme mostly found?

foetal tissue, the placenta and brain (-pituitary)

61

Where is type 1 de-iodinase enzyme mostly found?

liver and kidneys

62

How does T3 activate the TH receptor?

TH receptor is activated and travels to the nucleus of the cell where it binds with the RXR and a transcription factor

63

What are the 4 thyroid hormone receptor isoforms?

TRa1, TRa2, TRb1, TRb2

64

Which is the predominant form of thyroid hormone receptor in most tissues?

TRa

65

Which tissues is TRb the predominant form of thyroid hormone receptor?

liver and negative feedback loop

66

Test results show: high TSH, low fT4...diagnosis is...

primary hypothyroidism

67

Test results show: high TSH, normal fT4...diagnosis is...

subclinical hypothyroidism

68

Test results show: high TSH, high fT4...diagnosis is...

TSH secreting tumour or TH resistance

69

Test results show: high TSH, high fT4/ low fT3..diagnosis is...

deiodinase deficiency, TH antibody

70

Test results show: low TSH, high fT4/T3...diagnosis is...

primary hyperthyroidism

71

Test results show: low TSH, normal fT4...diagnosis is...

subclinical hyperthyroidism

72

Test results show: low TSH, low fT4...diagnosis is...

secondary hypothyroidism

73

Test results show: low TSH, lowfT4/T3...diagnosis is...

sick euthyroid or pituitary disease

74

Test results show: normal TSH, abnormal fT4...diagnosis is...

consider TBG, amiodarone, pituitary TSH tumour

75

Chief cause of hypothyroidism worldwide

iodine deficiency

76

Chief cause of hypothyroidism in the UK

Hashimotos disease

77

Clinical features of hypothyroidism that might be seen in the hair and skin (4+)

coarse, sparse hair; dull expressionless face; periorbital puffiness; pale cool skin that feels doughy

78

Clinical features involving thermogenesis of hypothyroidism

cold intolerance

79

Cardiac features of hypothyroidism

bradycardia, worsening heart failure

80

Metabolic features of hypothyroidism

hyperlipidaemia, weight gain, decreased appetite

81

Common GI feature of hypothyroidism

constipation

82

Common neurological features of hypothyroidism

depression, psychosis, carpal tunnel syndrome and decreased visual acuity

83

Common gynae features of hypothyroidism

menorrhagia follows by amenorrhoea

84

Goitrous causes of primary hypothyroidism (4)

chronic thyroiditis (Hashimotos), iodine deficiency, drug induced (lithium, amiodarone), maternally transmitted

85

Non-goitrous causes of primary hypothyroidism (3)

atrophic thyroiditis (autoimmune), post-ablative, congenital developmental defect

86

Subclinical hypothyroidism may present with what blood test features?

high TSH, normal T4

87

Common clinical investigations other than thyroid function tests which may be ordered when considering hypothyroidism

MCV - macrocytosis, increased CK, increased LDL and cholesterol, hyponatraemia, hyperprolactinaemia

88

Main drug treatment of hypothyroidism

levothyroxine (T4) - taken before breakfast

89

Why might levothyroxine dose need to be increased in pregnancy?

due to increased TBG produced by the liver

90

Why is it important to slowly restore normal thyroid function in hypothyroidism?

it may cause cardiac arrhythmias

91

Dose of levothyroxine in young person?

50-100µg/day

92

Dose of levothyroxine in elderly

25-50µg/day

93

Antibodies associated with Hashimoto's thyroiditis

anti-TPO - thyroid peroxidase

94

group most commonly affected by myxoedema coma

elderly women with longstanding or undiagnosed hypothyroidism

95

Signs of myxoedema coma

bradycardia, type 2 resp failure, hypoxia, hypercarbia, co-existing adrenal failure

96

cardiac features of hyperthyroidism

palpitations, AF, rarely cardiac failure

97

General feelings when suffering from hyperthyroidism

anxiety, irritibility, sleep disturbance

98

How might hyperthyroidism affect the sympathetic nervous system?

sweating and tremors

99

Visual features of hyperthyroidism

lid retraction (non-specific), diplopia, proptosis - Graves

100

Gynae features of hyperthyroidism

lighter and less frequent periods

101

Where might a patient experience weakness in hyperthyroidism?

thighs and upper arms

102

Thermogenesis in hyperthryoidism

heat intolerance

103

Weight in hyperthyroidism

decreased despite increased appetite

104

Causes of thyrotoxicosis associated with hyperthyroidism (7)

Graves, Hashitoxicosis, thyrotropinoma, thryoid cancer, toxic solitary nodule, toxic multinodular goitre

105

Causes of thyrotoxicosis associated with hyperthyroidism (3)

thyroid inflammation (post-partum, sub-acute, drug induced), exogenous TH, ectopic thyroid tissue

106

Age associated with Grave's disease

younger patients (20-50years)

107

Is there a genetic component to Graves?

Yes - 70% have susceptibility factors and sisters and children of women with Graves have a 5-8% chance of developing an autoimmune thyroid disease of any kind

108

Key exacerbating factor in Grave's disease

smoking - more severe and difficult to treat in smokers

109

Investigations in Graves disease

TFT
LFTs
Calcium
WCC
TSH receptor antibody

110

Thyroid function test results expected in Graves disease

Decreased TSH and increased fT3/T4

111

Expected LFTs and calcium results in Graves disease

hypercalcaemia and raised ALP due to increased bone turnover --> association with osteoporosis

112

Expected WCC in Graves disease

leucopaenia - often milk

113

TSH receptor antibody is confirmation of diagnosis of Graves - True/False

True - If this is present then there is no need to image the thyroid gland

114

Clinical signs of Graves disease (4)

Pretibial myxoedema, thyroid acropachy, thyroid bruit, graves eye disease

115

Graves eye disease occurs in what percentage of patients...what group are particularly high risk?

20%, particularly smokers

116

confirmation of graves eye disease on MRI

inflammation behind the eye

117

Which group of patients is most likely to experience nodular thyroid disease?

older patients - occurs with insidious onset

118

What features suggest a thyroid storm?

resp and cardiac collapse, severe hyperthermia, exaggerated reflexes

119

Patients at risk of thyroid storm?

those with acute infection or recent surgery

120

treatment of a thyroid storm?

Lugol's iodine, glucocorticoids, PTU, b-blockers, fluids and monitoring

121

Brief overview of deQuervains thyroiditis

subacture granulomatous thyroiditis, inflammation of thyroid which may be painful and oftern preceeded by a viral illness

122

3 phases of deQuervains thyroiditis

thyrotoxicosis, hypothyroid, euthryroid

123

investigation results confirming deQuervains thyroiditis

raised ESR, CRP and TH levels

124

First line treatment of hyperthyroidism

carbimazole

125

mechanism of action of treatment of hyperthyroidism

inhibition of thyroid peroxidase --> blocks TH synthesis

126

situation where carbimazole is not first line treatment

early pregnancy - may cause aplasia cutis

127

1st line treatment in early pregnancy for hyperthyroidism

polythiouracil (PTU) - 10x less potent than carbimazole

128

mechanism of action of PTU

inhibits DIO1

129

main risk of PTU

1:10000 liver failure

130

in the first 6 weeks of hyperthyroid treatment, what is the biggest side effect risk

agranulocytosis - warn verbally, get urgent FBC if fever, oral ulcer or oropharyngeal infection

131

common side effects of hyperthyroidism treatments

cholestatic jaundic, increased liver enzymes, fulminant liver failure