Pathology of the Thyroid

Question 1

from what does the thyroid develop?

Answer 1

evagination of pharyngeal epithelium

descent from foramen caecum to normal location along thyroglossal duct

Question 2

name 3 common abnormalities in the development of the thyroid?

Answer 2

failure of descent = lingual thyroid
excessive descent = retrosternal location in mediastinum
thyroglossal duct cyst

Question 3

what are thyroglossal duct cysts?

Answer 3

remnants of the thyroglossal duct

parts of ectopic thyroid tissue left behind as it descends - can become cystic

Question 4

describe the structure of thyroid tissue?

Answer 4

follicles surrounded by flat to cuboidal follicular epithelial cells
within the centre of each follicle is a colloid
occasional scattered C cells which secrete calcitonin

Question 5

what is a colloid?

Answer 5

dense amorphic pink material containing thyroglobulin

Question 6

where are thyroid hormones stored?

Answer 6

in the colloid

Question 7

what causes release of T3 and T4?

Answer 7

TRH from hypothalamus stimulates anterior pituitary to produce TSH which stimulates thyroid follicular epithelium to produce T3 and T4
T3 and T4 inhibit anterior pituitary and hypothalamus to switch off production

Question 8

how does TSH cause release of T3 and T4?

Answer 8

TSH binds to TSH receptor on surface of thyroid epithelial cells
G proteins activated with conversion of GTP to GDP and production of cAMP
cAMP increases production and release of T3 and T4
T3 and T4 circulate in bound and free forms
On release T3 and T4……………..

Question 9

4 types of thyroid pathology?

Answer 9

hyperthyroidism
hypothyroidism
goitre
neoplasia

Question 10

what are the most common forms of inflammatory thyroid disease?

Answer 10

auto-immune

• hashimotos thyroiditis (hypothyroidism)
• graves disease (hyperthyroidism)

Question 11

what else can cause inflsmmation in thyroid?

Answer 11

infection
palpation
subacute lymphocytic
de quervains

Question 12

what causes autoimmune thyroiditis?

Answer 12

familial
concordance in MZ twins
associated with HLA haplotype
polymorphisms in ummune regulation associated genes
- CTLA-4 (negative regulator of T cell response)
- PTPN-22 (inhibits T cell function)
associations with other autoimmune disease

Question 13

what is thyrotoxicosis?

Answer 13

excess of T3 and T4 (hyperthyroidism)

Question 14

what can cause thyrotoxicosis?

Answer 14

graves disease (85%)
hyperfunctioning nodules and tumours (adenomas)
TSH secreting pituitary adenoma (rare)
thyroiditis
ectopic production (struma ovarii)
factitious (self medicating with hormones, gland is normal)

Question 15

who does graves disease usually affect?

Answer 15

females

20-40 yrs old

Question 16

what is graves disease?

Answer 16

antibodies to TSH receptor, thyroid peroxisomes and thyroglobulin

Question 17

what are the anti TSH receptor antibodies in graves?

Answer 17

thyroid stimulating immunoglobulin (relatively specific, causes hyperfunctioning)
thyroid growth stimulating immunoglobulin
TSH binding inhibitor immunoglobulins

Question 18

triad of features in graves disease?

Answer 18

hyperthyroidism with diffuse enlargement of thyroid
eye changes (exophthalmos)
pretibial myxedema

Question 19

why is there lack of colloid seen in some hyperthyroidism cases?

Answer 19

colloid being continuously exported

Question 20

what causes hypothyroidism and who does it usually affect?

Answer 20

hashimotos
middle aged women
associated with other autoimmune disorders
associated with HLA-DR3 and DR5
iodine deficiency
drugs
post therapy
………….

Question 21

what is hashimotos?

Answer 21

gradual failure of thyroid function due to autoimmune desctruction of …………

Question 22

what are the antibodies in hashimotos?

Answer 22

anti-thyroglobulin and anti-peroxidase

- cause antibody dependant cell mediated cytotoxicity when bound

Question 23

mechanism in hashimotos?

Answer 23

……..

Question 24

what is hashitoxicosis?

Answer 24

transient release of thyroid hormone which sometimes precedes hashimotos

Question 25

….

Answer 25

…..

Question 26

what is goitre?

Answer 26

any enlargement of the thyroid
usually due to lack of iodine (dietary or bio-availability)
…

Question 27

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Question 32

what neoplasms can occur in the thyroid?

Answer 32

adenomas (follicular adenoma)

carcinomas (papillary, follicular, medullary, anaplastic)

Question 33

what are the features of thyroid adenoma?

Answer 33

discrete solitary mass
incidental finding
can cause dysphagia
…………
usually non-functional
can secrete thyroid hormones (thyrotoxicosis)
can present similar to dominant nodule in multinodular goitre or ……carcinoma

Question 34

what causes thyroid adenoma?

Answer 34

few have mutant ras or PIK3CA

……

Question 35

who do thyroid carcinomas affect?

Answer 35

any age group

female predominance in adults

Question 36

where are most thyroid cancers derived from?

Answer 36

follicular epithelium (medullary from C cells)

Question 37

aetiology

Answer 37

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Question 39

what is the most common thyroid cancer?

Answer 39

papillary carcinoma

Question 40

describe papillary carcinoma?

Answer 40

solitary nodule in thyroid
can be multifocal
often cystic
may be calcified
can be present with lymph node metastases
…………………….

Question 41

how does papillary carcinoma present?

Answer 41

lesion in thyroid gland or cervical lymph node mass
local effects
- hoarseness
- dysphagia
- cough
- dyspnoea
sometimes haematogenous spread to lung
………...

Question 42

second most common thyroid cancer?

Answer 42

follicular carcinoma

Question 43

features of follicular carcinoma?

Answer 43

usually females
usually single nodule
slowly enlarging, painless, non-functional
lymphatic spread is rare
haematogenous spread to bone, lungs and liver

Question 44

invasive growth pattern of follicular carcinoma?

Answer 44

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