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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
What are the main features of T4 and T3?
T4 is secreted more | T3 is more biologically active
26
What is the simple version of T3 and T4 synthesis with + and -?
TRH from hypothalamus + TSH from pituitary gland + follicular cell in thyroid gland secrete T3 and T4 which then - TRH and TSH production
27
How are the hormones transported around the body?
- bound by TBG, TBPA or albumin | - the rest is unbound and this is the metabolically active part
28
What effects do the thyroid hormones have?
- 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
What are the symptoms of hyperthyroidism?
- 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
Where do each of the types of deiodinases act?
- Type 1 = liver and kidney - Type 2 = heart, skeletal muscle, CNS, fat, thyroid and pituitary - Type 3 = fetal tissue, placenta and brain
31
What are the most common benign presentations in the thyroid?
- cyst - colloid nodule - benign follicular adenoma - hyperplastic nodule
32
What is the treatment for lymphoma?
- steroids - chemotherapy - radiotherapy
33
What is the order of the cartilages in the neck area?
Hyoid Thyroid Cricoid (high tie? cry!)
34
What are the key things to remember in a thyroid investigation?
- history: neck irradiation + FHx of thyroid cancer - exam: neck nodes + hoarseness - investigation: TSH + USS-FNA
35
What are the types of treatment for thyroid lumps?
- low risk lobectomy of one wing | - higher risk total thyroidectomy and maybe give RAI to destroy remaining thyroid cells
36
What is the follow-up test after thyroid removal to test for if the surgery has been a success?
check thyroglobulin levels
37
What is a CT scan used to show in a multi-nodular goitre?
- retrosternal extension | - tracheal compression that can cause stridor
38
What is primary disease of the thyroid?
disease of the thyroid itself with or without goitre which is usually autoimmune in cause
39
What is secondary disease of the thyroid?
the thyroid is normal but there is hypothalamic or pituitary disease
40
Where are each of the hormones associated with?
TRH - hypothalamus TSH - pituitary T4 - thyroid T4 --> T3 - liver
41
What are the hormone levels in primary hypothyroidism?
LOW T3 and T4 | HIGH TSH
42
What are the hormone levels in primary hyperthyroidism?
HIGH T3 and T4 | LOW TSH
43
What are the hormone levels in secondary hypothyroidism?
LOW T3 and T4 | LOW TSH
44
What are the hormones levels in secondary hyperthyroidism?
HIGH T3 and T4 | HIGH TSH
45
What is myxoedema?
severe hypothyroidism (pretibial myxoedema is Graves' disease which is hyper)
46
What are the main categories for causes or primary hypothyroidism?
- goitre: Hashimoto's thyroiditis, iodine deficiency and drugs - non-goitre: atrophic thyroiditis and iatrogenic - self-limiting: post partum or subacute
47
What are the symptoms of hypothyroidism?
- 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
What is the medical hypothyroidism emergency?
Myxoedema coma - severe disease - elderly woman with undiagnosed or untreated disease - causes serious heart arrhythmias and type 2 respiratory failure
49
What is thyrotoxicosis?
when there is excess thyroid hormone and the biological process of what happens
50
What is the main cause of hyperthyroidism?
- Graves' diseases in a young patient | - Toxic multi nodular goitre in an older patient
51
What is the main medical emergency for hyperthyroidism?
thyroid storm which results in respiratory and cardiac collapse
52
What can be the causes of thyroiditis?
subacute and triggered by an infection
53
What are the levels of hormone in subclinical thyroid disease?
abnormal TSH with normal thyroid hormone levels
54
What are the features of differentiated thyroid cancer?
- hard to diagnose - good outcome - takes up iodine - secretes thyroglobulin

My Endocrinology (12 decks)

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