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Endocrine lectures > thyroid pathology > Flashcards

thyroid pathology Flashcards

1
Q

where does the thyroid develop from?

A

evagination of pharyngeal epithelium

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2
Q

where does the thyroid descend from?

A

foramen caecum

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3
Q

what are some embryological abnormalities of the thyroid?

A

Failure of descent – lingual thyroid
Excessive descent – retrosternal location in mediastinum
Thyroglossal duct cyst

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4
Q

what is the thyroid composed of?

A

lobules defined by thin fibrous septa each containing follicles.
Each follicle surrounded by flat to cuboidal follicular epithelial cells.
Within the centre of each follicle is dense amorphous pink material containing thyroglobulin

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5
Q

what do C cells in the thyroid secrete?

A

calcitonin which results in lower serum Ca levels

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6
Q

what does TSH bind to?

A

TSH receptor on surface of thyroid epithelial cells.

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7
Q

what do G proteins do in terms of thyroid function?

A

G proteins activated with conversion of GTP to GDP and production of cAMP.

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8
Q

what does cAMP do?

A

increase prodcution and release of T3 and T4

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9
Q

T3 and T4 bind to receptors in target cells and then what?

A

Complex translocates to the nucleus
Binds to Thyroid Response Elements on target genes
Stimulates transcription of these genes
Increase BMR

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10
Q

what stimulates the release of TSH from the anterior pituitary?

A

TRH from the hypothalamus

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11
Q

name some thyroid pathology?

A

Thyroiditis
Hypothyroidism / Hyperthyroidism /
Thyrotoxicosis
Goitre
Neoplasia

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12
Q

what is an example of hypothroid function?

A

Hashimoto’s thyroiditis

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13
Q

what is an example of hyperthyroid function?

A

graves disease

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14
Q

what are the features of thyroiditis?

A

Increased incidence in family members
Concordance rate in MZ twins high
Susceptibility associated with HLA haplotype
Polymorphisms in immune regulation associated genes
CTLA-4
Negative regulator of T cell responses
Polymorphisms with reduced protein
level / function increase risk of auto-
immune disease
PTPN-22
Inhibits T cell function
Association with other auto-immune diseases

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15
Q

what are the features of Hashimotos thyroiditis?

A

Gradual failure of thyroid function
Auto immune destruction of thyroid tissue
10-20F:1M
45 - 60 years old
Genetic background
Twin studies
Auto ab in asymptomatic siblings

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16
Q

immune features of hashimotos thyroiditis?

A

Anti-thyroid antibodies
Anti-thyroglobulin and anti-peroxidase
When bound cause antibody dependent
cell mediated cytotoxicity
CD8 +ve cells may mediate destruction of thyroid epithelium
Cytokine mediated cell death
gamma interferon from T cell activation
recruits macrophages that may damage
thyroid follicles

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17
Q

what are the symptoms and signs of hypothyroidism due to?

A

low levels of T3 and T4

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18
Q

who is usually affected by hypothyroidism?

A

middle aged women
associated with other autoimmune diseases
associated with HLA-DR3 and DR5

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19
Q

how does hypothyroidism occur?

A

iodine deficiency, drugs (lithium etc), post therapy (surgery, 131I, irradiation) , congenital abnormalities & in born errors of metabolism

Rarely a result of secondary (pituitary) or tertiary (hypothalamic) pathology

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20
Q

what are the features of graves disease?

A

Autoimmune disorder, 10F:1M, 20-40 years old
Antibodies to TSH receptor, thyroid peroxisomes and thyroglobulin
Anti TSH receptor antibodies

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21
Q

what are the main causes of hyperthyroidism?

A

85% are due to Grave’s disease
Other thyroid causes include hyperfunctioning nodules & tumours (adenoma, carcinoma)
TSH secreting pituitary adenoma (rare)

22
Q

what causes the symptoms and signs of hyperthyroidism?

A

excess T3 and T4

23
Q

what are the triad of graves disease features?

A

Hyperthyroidism with diffuse enlargement of the thyroid
Eye changes (exophthalmos)
Pretibial myxoedema.

24
Q

what causes the eye changes in graves disease?

A

fibroblasts etc that express TSH receptors

25
Q

what is goitre?

A

Any enlargement of the thyroid gland

26
Q

where does goitre usually occur?

A

Commonly applied to the processes of diffuse and multinodular goitre
Disorders most often due to a lack of
dietary iodine
May be due to lack of bio-availability of
iodine

27
Q

what can cause goitre?

A

reduced T3/T4 production which causes a rise in TSH, stimulating gland enlargement

28
Q

what % of the population are affected by goitre?

A

10%

29
Q

who is most affected by goitre?

A

more females than males
occurs in puberty and in young adults

30
Q

is TSH raised in diffuse goitre

A

no its normal

31
Q

was is multi nodular goitre?

A

Evolution from long standing simple goitre
Recurrent hyperplasia and involution
Enlargement can be impressive

32
Q

what is the risk of malignancy in multinodular goitre?

A

low (<5%)

33
Q

what are the common tumours of the thyroid?

A

Adenomas
Follicular Adenoma
Carcinomas
Papillary (75-85%)
Follicular (10-20%)
Anaplastic (<5%)
Medullary (5%)

34
Q

what are the features of adenomas?

A

Discrete solitary mass
Incidental finding
If large local symptoms eg dysphagia
Encapsulated by a surrounding collagen cuff
Composed of neoplastic thyroid follicles i.e. Follicular Adenoma

35
Q

what are adenomas difficult to distinguish from?

A

Dominant nodule in multinodular goitre
Follicular carcinoma

36
Q

do adenomas secrete thyroid hormones?

A

yes - thyrotoxicosis

37
Q

what are the features of carcinomas?

A

1.5% all cancers
Can affect any age group : childhood to elderly
Female predominance (except childhood & elderly)
Important differences in aetiology, and clinical behaviour of different types of thyroid cancers

38
Q

what is the most common form of thyroid cancer?

A

papillary carcinoma

39
Q

how do papillary carcinomas look?

A

Usually solitary nodule in thyroid
Can be multifocal
Often cystic
May be calcified : psammoma bodies

40
Q

can papillary carcinoma present with lymphnode metastases?

A

yes

41
Q

how do papillary carcinomas present?

A

Lesion in thyroid gland or cervical lymph node mass (metastasis)
Local effects:
Hoarseness
Dysphagia
Cough
Dyspnoea
All suggest locally advanced disease

42
Q

what is the survival rate of papillary carcinoma?

A

at 10 years >95%

43
Q

what is the second most common thyroid carcinoma?

A

follicular

44
Q

what are the people that follicaular carcinoma usually affects?

A

females more than males
older (40s and 50s)

45
Q

what is more common in follicular carcinoma-haematogenous or lymphatic spread?

A

haematogenous

46
Q

are follicular carcinomas invasive?

A

yes

47
Q

what is the survival rate of follicular carcinoma?

A

50% at 10 years

48
Q

what are MTC cancers derived from

A

C cells (neuroendocrine)

49
Q

what is the 10 year survival rate of medullary cancers?

A

73 %

50
Q

what are the features of anaplastic carcinoma?

A

Undifferentiated and aggressive tumours

Usually older patients

May occur in people with a history of differentiated thyroid cancer

Rapid growth and involvement of neck structures and death

Endocrine lectures (32 decks)

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