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
what is goitre?
Any enlargement of the thyroid gland
26
where does goitre usually occur?
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
what can cause goitre?
reduced T3/T4 production which causes a rise in TSH, stimulating gland enlargement
28
what % of the population are affected by goitre?
10%
29
who is most affected by goitre?
more females than males occurs in puberty and in young adults
30
is TSH raised in diffuse goitre
no its normal
31
was is multi nodular goitre?
Evolution from long standing simple goitre Recurrent hyperplasia and involution Enlargement can be impressive
32
what is the risk of malignancy in multinodular goitre?
low (<5%)
33
what are the common tumours of the thyroid?
Adenomas Follicular Adenoma Carcinomas Papillary (75-85%) Follicular (10-20%) Anaplastic (<5%) Medullary (5%)
34
what are the features of adenomas?
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
what are adenomas difficult to distinguish from?
Dominant nodule in multinodular goitre Follicular carcinoma
36
do adenomas secrete thyroid hormones?
yes - thyrotoxicosis
37
what are the features of carcinomas?
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
what is the most common form of thyroid cancer?
papillary carcinoma
39
how do papillary carcinomas look?
Usually solitary nodule in thyroid Can be multifocal Often cystic May be calcified : psammoma bodies
40
can papillary carcinoma present with lymphnode metastases?
yes
41
how do papillary carcinomas present?
Lesion in thyroid gland or cervical lymph node mass (metastasis) Local effects: Hoarseness Dysphagia Cough Dyspnoea All suggest locally advanced disease
42
what is the survival rate of papillary carcinoma?
at 10 years >95%
43
what is the second most common thyroid carcinoma?
follicular
44
what are the people that follicaular carcinoma usually affects?
females more than males older (40s and 50s)
45
what is more common in follicular carcinoma-haematogenous or lymphatic spread?
haematogenous
46
are follicular carcinomas invasive?
yes
47
what is the survival rate of follicular carcinoma?
50% at 10 years
48
what are MTC cancers derived from
C cells (neuroendocrine)
49
what is the 10 year survival rate of medullary cancers?
73 %
50
what are the features of anaplastic carcinoma?
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