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My Endocrinology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

How does the thyroid develop?

A
  • from the pharyngeal epithelium (thickening at the back of the tongue)
  • descends along the thyroglossal duct in 4th week of development
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2
Q

How can the development of the thyroid go wrong?

A
  • failure of descent
  • excessive descent
  • thyroglossal duct cyst
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3
Q

What is the thyroid made up of?

A
  • two lobules with follicles inside which make thyroglobulin

- some parafollicular cells that secrete calcitonin

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4
Q

How does TSH cause metabolism?

A
  • TSH binds to TSH receptor so cAMP is made
  • cAMP increases production and release of T3+4
  • this changes the amount of transcription of certain genes
  • these genes encourage lipid and carbohydrate metabolism
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5
Q

What are the autoimmune causes of thyroid changes?

A
  • hypofunction: Hashimoto’s thyroiditis

- hyperfunction: Grave’s disease

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6
Q

What are the features of hyperthyroidism?

A
  • excess T3 and T4
  • usually due to Grave’s
  • there is enhanced hormone release
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7
Q

What happens in Grave’s disease?

A

autoimmune antibodies to the TSH receptor, thyroid peroxisomes and thyroglobulin

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8
Q

What is the triad of Grave’s disease?

A
  • hyperthyroid
  • eye changes
  • pretibial myxoedema
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9
Q

What happens in Hashimoto’s thyroiditis?

A
  • autoimmune destruction of thyroid tissue leading to thyroid failure
  • involves anti-thyroglobulin and anti-peroxidase
  • there are TPO antibodies (thyroid peroxidase)
  • large damaged thyroid and a lymphoid infiltrate
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10
Q

What can sometimes happen transiently in Hashimoto’s?

A

there can be transient hyperfunction called Hashitoxicosis

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11
Q

What is goitre?

A
  • enlargement of the thyroid gland

- reduced T3/4 production so there is a rise in TSH so gland enlargement

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12
Q

What does a diffuse goitre usually suggest?

A

euthyroid

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13
Q

What are the most likely thyroid neoplasia?

A
  • benign= adenoma

- malignant= papillary, follicular, medullary and anaplastic

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14
Q

What are the features of adenomas?

A
  • solitary masses that are found incidentally

- encapsulated in a collagen cuff

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15
Q

What are the features of carcinomas?

A
  • well differentiated

- derived from follicular epithelium

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16
Q

What are the features of papillary carcinomas?

A
  • most common
  • sometimes present with lymph node metastasis
  • causes hoarseness, dysphagia, cough and dyspnoea
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17
Q

What are the features of follicular carcinoma?

A
  • single nodule
  • haematogenous spread
  • widely or minimally invasive based on capsule invasion
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18
Q

What are the features of medullary carcinoma?

A
  • rare
  • sporadic
  • present as neck mass with paraneoplastic syndrome
  • calcitonin is the tumour cell marker
  • four types
  • MEN association
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19
Q

What are the features of anapaestic carcinoma?

A

aggressive disease in old people

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20
Q

What are the unique features of the thyroid gland?

A
  • only palpable endocrine gland

- only gland that needs substances from the environment to make hormones

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21
Q

What is the pathway for thyroid hormone synthesis?

A

thyroglobulin made –> iodide transport from blood into follicular cells by active transport –> I- oxidised to I –>iodine moves to colloid where thyroglobulin is –> iodine attaches to thyroglobulin at tyrosine –> either monoiodotyrosin (MIT) or di-iodotyrosin (DIT) is made

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22
Q

What comes together to make T3?

A

MIT + DIT –> T3

23
Q

What comes together to make T4?

A

DIT + DIT –> T4

24
Q

What happens to the T3 and T4 once it is made?

A

stored in colloid thyroglobulin until required

25
Q

What are the main features of T4 and T3?

A

T4 is secreted more

T3 is more biologically active

26
Q

What is the simple version of T3 and T4 synthesis with + and -?

A

TRH from hypothalamus + TSH from pituitary gland + follicular cell in thyroid gland secrete T3 and T4 which then - TRH and TSH production

27
Q

How are the hormones transported around the body?

A
  • bound by TBG, TBPA or albumin

- the rest is unbound and this is the metabolically active part

28
Q

What effects do the thyroid hormones have?

A
  • increase metabolic rate and glucose uptake
  • more glucose made by the liver
  • less fat is made
  • increase RR and HR
  • increase metabolism of carbohydrate, lipid and protein
29
Q

What are the symptoms of hyperthyroidism?

A
  • diarrhoea
  • sweaty skin
  • weight loss
  • light and less frequent periods
  • anxiety and nervousness
  • palpitations
  • tremor
  • double vision
  • lid retraction
  • proptosis
  • hard change
  • muscle weakness
  • heat intolerance
30
Q

Where do each of the types of deiodinases act?

A
  • Type 1 = liver and kidney
  • Type 2 = heart, skeletal muscle, CNS, fat, thyroid and pituitary
  • Type 3 = fetal tissue, placenta and brain
31
Q

What are the most common benign presentations in the thyroid?

A
  • cyst
  • colloid nodule
  • benign follicular adenoma
  • hyperplastic nodule
32
Q

What is the treatment for lymphoma?

A
  • steroids
  • chemotherapy
  • radiotherapy
33
Q

What is the order of the cartilages in the neck area?

A

Hyoid
Thyroid
Cricoid
(high tie? cry!)

34
Q

What are the key things to remember in a thyroid investigation?

A
  • history: neck irradiation + FHx of thyroid cancer
  • exam: neck nodes + hoarseness
  • investigation: TSH + USS-FNA
35
Q

What are the types of treatment for thyroid lumps?

A
  • low risk lobectomy of one wing

- higher risk total thyroidectomy and maybe give RAI to destroy remaining thyroid cells

36
Q

What is the follow-up test after thyroid removal to test for if the surgery has been a success?

A

check thyroglobulin levels

37
Q

What is a CT scan used to show in a multi-nodular goitre?

A
  • retrosternal extension

- tracheal compression that can cause stridor

38
Q

What is primary disease of the thyroid?

A

disease of the thyroid itself with or without goitre which is usually autoimmune in cause

39
Q

What is secondary disease of the thyroid?

A

the thyroid is normal but there is hypothalamic or pituitary disease

40
Q

Where are each of the hormones associated with?

A

TRH - hypothalamus
TSH - pituitary
T4 - thyroid
T4 –> T3 - liver

41
Q

What are the hormone levels in primary hypothyroidism?

A

LOW T3 and T4

HIGH TSH

42
Q

What are the hormone levels in primary hyperthyroidism?

A

HIGH T3 and T4

LOW TSH

43
Q

What are the hormone levels in secondary hypothyroidism?

A

LOW T3 and T4

LOW TSH

44
Q

What are the hormones levels in secondary hyperthyroidism?

A

HIGH T3 and T4

HIGH TSH

45
Q

What is myxoedema?

A

severe hypothyroidism (pretibial myxoedema is Graves’ disease which is hyper)

46
Q

What are the main categories for causes or primary hypothyroidism?

A
  • goitre: Hashimoto’s thyroiditis, iodine deficiency and drugs
  • non-goitre: atrophic thyroiditis and iatrogenic
  • self-limiting: post partum or subacute
47
Q

What are the symptoms of hypothyroidism?

A
  • decreased appetitie
  • depression
  • abnormal/more periods
  • coarse and sparse hair
  • dull face
  • periorbital puffiness
  • pale cool skin
  • sleep apnoea
  • vitiligo
  • constipation
  • cold intolerance
  • decreased HR
  • pitting oedema
  • pericardial effusion
  • increased lipids
48
Q

What is the medical hypothyroidism emergency?

A

Myxoedema coma

  • severe disease
  • elderly woman with undiagnosed or untreated disease
  • causes serious heart arrhythmias and type 2 respiratory failure
49
Q

What is thyrotoxicosis?

A

when there is excess thyroid hormone and the biological process of what happens

50
Q

What is the main cause of hyperthyroidism?

A
  • Graves’ diseases in a young patient

- Toxic multi nodular goitre in an older patient

51
Q

What is the main medical emergency for hyperthyroidism?

A

thyroid storm which results in respiratory and cardiac collapse

52
Q

What can be the causes of thyroiditis?

A

subacute and triggered by an infection

53
Q

What are the levels of hormone in subclinical thyroid disease?

A

abnormal TSH with normal thyroid hormone levels

54
Q

What are the features of differentiated thyroid cancer?

A
  • hard to diagnose
  • good outcome
  • takes up iodine
  • secretes thyroglobulin

My Endocrinology (12 decks)

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