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Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What is the thyroid?

A

A highly vascular butterfly shaped endocrine organ

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2
Q

Where does the thyroid sit?

A

Anterior to the trachea

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3
Q

How many lobes is the thyroid made up of?

A

2

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4
Q

What are the two lobes joined together by?

A

Isthmus

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5
Q

What is on the posterior side of the thyroid?

A

4 smaller glands known as the parathyroid glands

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6
Q

What is the thyroid attached to?

A

The thyroid cartilage and upper end of trachea

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7
Q

What happens to the thyroid on swallowing?

A

It moves

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8
Q

What are the two different types of cells that make up the thyroid?

A

Parafollicular C cells and follicular cells

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9
Q

What do the follicles encase?

A

The colloid

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10
Q

What is the follicle made up of?

A

Follicular cells

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11
Q

Where are the parafollicular cells located?

A

Adjacent to follicular cells

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12
Q

What do the parafollicular cells lie within?

A

Connective tissue

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13
Q

What do follicular cells produce?

A

thyroglobulin

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14
Q

What do parafollicular C cells produce?

A

Calcitonin

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15
Q

Where is thyroglobulin stored?

A

In the colloid

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16
Q

What is taken up by the follicular cells and extruded into the colloid?

A

Iodine

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17
Q

What occurs at the colloid resulting in release of thyroglobulin?

A

Pinocytosis

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18
Q

How are thyroid hormones produced from thyroglobulin?

A

Thyroglobulin is acted on by lysosomes within follicular cells

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19
Q

What are the two hormones produced in the thyroid?

A

T3 (triiodothyronine) and T4 (thyroxine)

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20
Q

What does iodine attach to on thyroglobulin?

A

Tryosine residues

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21
Q

What is formed when iodine attaches to tyrosine residues?

A

MIT and DIT

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22
Q

What are MIT and DIT?

A

Building blocks of thyroid hormones

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23
Q

How many MITs and DITs are T3 and T4 made up of?

A

T3 - 2 x MIT

T4 - MIT + DIT

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24
Q

What is the majority of secreted hormones?

A

T4

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25
Q

What is more biologically active, T3 or T4?

A

T3

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26
Q

How are thyroid hormones in their active state?

A

Unbound

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27
Q

What is T4 converted to by the liver and kidneys?

A

T3

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28
Q

What are the majority of inactive thyroid hormones bound to?

A

Albumin

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29
Q

What are thyroid hormones responsible for maintaining?

A

Metabolism, growth, reproduction, behaviour and development

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30
Q

What do thyroid hormones work in conjunction with when controlling metabolism?

A

Growth hormone

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31
Q

What effect do thyroid hormones have on metabolism?

A

Increase protein synthesis and increase glucose and fatty acid plasma levels

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32
Q

What other functions do thyroid hormones have besides metabolism?

A

role in thermogenesis, brain development in neonates, CNS activity, maintain bone turnover and gut motility

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33
Q

What effect does growth hormone have on fat tissue?

A

Increases lipolysis - increases plasma fatty acids

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34
Q

What effect does growth hormone have on the liver?

A

Increases gluconeogenesis - increases plasma glucose

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35
Q

What effect does growth hormone have on muscle?

A

Protein synthesis - decreases plasma AAs

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36
Q

What is the role of thyroid hormones in the nervous system?

A

Increase responsiveness to neurotransmitters

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37
Q

How do thyroid hormones increase responsiveness to neurotransmitters?

A

Increase the number of receptors to these transmitters

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38
Q

What two hormones regulate thyroid hormones?

A

TRH and TSH

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39
Q

Where is TSH released from?

A

Anterior pituitary

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40
Q

Where is TRH released from?

A

Hypothalamus

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41
Q

What effect does T3 have on the hypothalamus and anterior pituitary?

A

Negative feedback

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42
Q

Where does TRH have an effect?

A

On anterior pituitary to release TSH

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43
Q

Where does TSH have an effect?

A

On thyroid gland to release T3 and T4

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44
Q

What effect does hyperthyroidism have on the heart?

A

Increased force and rate

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45
Q

What cardiac symptoms will a hyperthyroidism patient experience?

A

Arrhythmias such as AF and tachycardia and palpitations

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46
Q

What complications arise from heat intolerance?

A

Moist, itchy skin

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47
Q

What is a temperature symptom in a hyperthyroidism patient?

A

Heat intolerance

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48
Q

What is the key thing about hyperthyroidism symptoms?

A

Everything is in overdrive

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49
Q

What happens to a patient with hyperthyroidisms weight and why?

A

They will lose weight - BMR increases

50
Q

What symptoms does a hyperthyroidism patient to do with movement?

A

Tremor and hyperkinesis

51
Q

What behaviour changes does someone with hyperthyroidism have?

A

Agitation, anxiety, restlessness

52
Q

What sleep changes does someone with hyperthyroidism have?

A

They may find it difficult to sleep - due to agitation and lots of energy

53
Q

What changes can occur to the menstrual cycle in someone with hyperthyroidism?

A

Irregular periods (oligomenorrhoea), loss of libido

54
Q

What is the main cause of hyperthyroidism?

A

Graves disease

55
Q

What is graves disease?

A

An autoimmune disease

56
Q

Who does graves disease usually affect?

A

Middle aged women

57
Q

How does graves disease cause hyperthyroidism?

A

Thyroid gland is stimulated by an autoantibody - not suppressed by high T3 and T4 levels

58
Q

What is TSI?

A

thyroid stimulation immunoglobulin produced in graves disease which acts in the same way as TSH

59
Q

What are the normal thyroid function levels?

A

TSH (0.4 - 4)
T3 (9.9 - 22)
fT4 (0.9 - 2.6)

60
Q

What are the typical thyroid function levels in someone with graves disease?

A

TSH

61
Q

Which thyroid hormone will always be raised in Graves disease?

A

T4

62
Q

Why is the TSH low in graves disease?

A

There are high levels of T3 and T4 which have a negative effect on TSH secretion

63
Q

What are the three main complications only seen in graves disease?

A

Eye disease (eyes bulging), pretibial myxoedema and a goitre

64
Q

When does eye disease appear in graves?

A

1-2 years after diagnosis

65
Q

Why is there eye bulging in graves disease?

A

There are receptors within the tissue and muscle surrounding the eyeball which are similar to TSH receptors - stimulated by TSI - leads to retro-orbital swelling due to inflamm response

66
Q

What causes loss of eye function in graves?

A

Collagen fibres being deposited in the muscle and tissue surrounding the eye

67
Q

What are the eye symptoms in graves?

A

Difficulty in eye movement, eye bulging, eyes feel gritty, blurred vision, redness of eyes and decreased colour vision

68
Q

When does pretibial myxoedema occur in graves?

A

1-2 years after diagnosis

69
Q

What is pretibial myxoedema?

A

Bilateral plaque formation on the anterior surface aspect of the lower legs

70
Q

What does pretibial myxoedema distinctly look like?

A

Orange peel - non-pitting

71
Q

When is pretibial myxoedema usually present in graves?

A

When the patient also has eye disease

72
Q

What is a goitre?

A

Swelling of the thyroid gland producing a neck lump which can be easily seen and palpated

73
Q

What can a goitre cause?

A

Compression of local structures - difficulty in breathing and swallowing

74
Q

What is a GI symptom in hyperthyroidism?

A

Diarrhoea

75
Q

What are the important things to note when examining a goitre?

A

Movement, nodules, size, bruit

76
Q

What other examinations besides a goitre examination should be done in a patient with suspected hyperthyroidism?

A

Lid-lag, eye movement, lower legs should be examined

77
Q

What is the second most common cause of hyperthyroidism?

A

Toxic multi nodular goitre

78
Q

What is TMG?

A

Presence of functioning autonomous nodules that secrete large amounts of thyroid hormones

79
Q

Where is TMG common?

A

Areas where population is iodine deficient

80
Q

Is a function adenoma or carcinoma more likely?

A

Adenoma

81
Q

What is de Quervain’s thyroiditis?

A

Hyperthyroidism initially caused by an acute inflamm process, usually viral in origin

82
Q

What other symptoms besides the classic hyperthyroid symptoms are seen in de Quervain’s thyroiditis?

A

Fever, malaise and local tenderness around thyroid gland

83
Q

What will the blood tests show in de Quervain’s thyroiditis?

A

In acute phase - hyperthyroidism

84
Q

What follows acute phase in de Quervain’s thyroiditis?

A

Transient hypothyroidism before patient goes back to euthyroid state

85
Q

What are the symptoms of hypothyroidism?

A

Opposite to those in hyperthyroidism - weight gain, slow reflexes, cold intolerance, fatigue, lethargy and increased soft tissue of face, hands and feet

86
Q

What are the symptoms of hypothyroidism not opposite to those in hyperthyroidism?

A

Coarse sparse hair, expressionless face, cool doughy skin, obstructive sleep apnoea

87
Q

What do the thyroid function tests show in hypothyroidism?

A

TSH - 45
T3 - 0.03
fT4 - 4

88
Q

What can hypothyroidism be separated into?

A

Primary and secondary causes

89
Q

What are the two kinds of hypothyroidism with primary causes?

A

Goitrous

Non-goitrous

90
Q

What are the two kinds of hypothyroidism with secondary causes?

A

Hypothalamic and pituitary

91
Q

What is the main cause of hypothyroidism?

A

Iodine deficiency

92
Q

What is Hashimoto’s thyroiditis?

A

Autoimmune disease causing hypothyroidism

93
Q

What do the antibodies attack in Hashimoto’s thyroiditis?

A

Thyroid peroxidase (amongst others) which is an enzyme used in the production of thyroid hormones

94
Q

Besides TPO what else do antibodies attack in Hashimoto’s thyroiditis?

A

Thyroglobulin - leads to destruction of the follicular cells of thyroid

95
Q

How does the thyroid gland feel in Hashimoto’s thyroiditis?

A

Rubbery, may range from feeling soft to hard

96
Q

What can cause widespread deficiency or loss of function of either the hypothalamus or the pituitary gland?

A

Infiltration, infection or malignancy of the glands

97
Q

What is the most likely diagnosis when theres increased TSH and decreased T4?

A

Hypothyroidism

98
Q

What is the most likely diagnosis when theres decreased TSH and increased T3/T4?

A

Hyperthyroidism

99
Q

What is the most likely diagnosis when theres decreased TSH with normal T4 and T3?

A

Subclinical hyperthyroidism

100
Q

What is the most likely diagnosis when theres increased TSH and normal T4?

A

Treated hypothyroidism

101
Q

What is the most likely diagnosis when theres decreased TSH and decreased T4 and T4?

A

Pituitary disease

102
Q

What test is useful for Hashimotos thyroiditis and graves disease?

A

Anti-thyroid antibodies

103
Q

What test is done if there is a goitre present and pathology is unknown?

A

Fine needle aspirate

U/s or thyroid scan

104
Q

What does a U/S scan of a goitre do?

A

Allows us to determine whether nodule is solid or cyst like

105
Q

What does a radioactive thyroid scan of a goitre do?

A

Distinguishes function or non-functioning nodules

106
Q

What is the initial therapy of hyperthyroidism?

A

Medical treatment

107
Q

What does medical treatment of hyperthyroidism involve?

A

Inhibition of the production of thyroid hormones from within the gland itself

108
Q

What are the drugs used in medical treatment of hyperthyroidism?

A

Carbimazole and propylthiouracil (PTU)

109
Q

How are the drugs in hyperthyroidism used?

A

Started at high dose initially and then gradually reduced over 12-18 months

110
Q

What is it important to check over the course of medical treatment of hyperthyroidism?

A

Circulating hormone levels - patient may become hypothyroid

111
Q

What is the major side effect of carbimazole?

A

Agranulocytosis

112
Q

When should a patient immediately stop taking carbimazole?

A

If they develop a dry cough or sore throat

113
Q

Besides medications for treatment of hyperthyroidism what other drugs are given?

A

Beta blockers - reduce effect of thyroid hormones on heart

114
Q

What surgery is done in hyperthyroidism?

A

Sub-total thyroidectomy

115
Q

What happens before a sub-total thyroidectomy?

A

Patient stops anti-thyroid drug treatment two weeks before

116
Q

What is the risk of a sub-total thyroidectomy?

A

Patient becoming hypothyroid

117
Q

Besides drugs and surgery what is another treatment done in hyperthyroidism?

A

Radio-iodine therapy

118
Q

What is radio-iodine therapy?

A

Radioactive iodine 131 is taken orally to destroy cells within the thyroid gland

119
Q

What happens to most patients who undergo radio-iodine therapy?

A

They become hypothyroid and require thyroid replacement therapy

120
Q

What is the treatment of hypothyroidism?

A

Replacement therapy of thyroid hormones

121
Q

What drug is given in hypothyroidism?

A

An analogue of thyroxine - levothyroxine

122
Q

How long will a patient be on levothyroxine?

A

The rest of their life

Endocrinology (6 decks)

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