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Y2 - Endocrine > Thyroid Pathology > Flashcards

Thyroid Pathology Flashcards

1
Q

What is the location of the thyroid gland?

A

In the anterior neck below the larynx along the thyroglossal duct

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2
Q

What is the histological structure of the thyroid gland?

A

Composed of lobules containing follicles defined by thin fibrous septa
Each follicle is surrounded by follicular epithelial cells
There are C cells (parafollicular cells) scattered about - these are slightly larger cells with clearer cytoplasm

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3
Q

What is the function of follicular cells?

A

Secrete thyroglobulin
Produce colloid and thyroid hormones
Control the release of these hormones into the blood

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4
Q

What is the function of C cells?

A

Secrete calcitonin

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5
Q

What is the process of secretion of thyroid hormones?

A

TSH from the pituitary gland binds to TSH G-protein coupled receptors on thyroid epithelial cells
This causes an increase in the production of cAMP
cAMP increases production and release of T3 and T4

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6
Q

What is the function of T3 and T4?

A

Bind to rage cells to increase basal metabolic rate

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7
Q

Describe the negative feedback effect that controls the secretion of thyroid hormones.

A

Hypothalamus releases TRH which stimulates the anterior pituitary gland to secrete TSH
TSH stimulates thyroid follicular epithelium to secrete T3 and T4
Increased levels of T3 and T4 inhibit the anterior pituitary gland and the hypothalamus to decrease the secretion of TSH and TRH

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8
Q

What do TRH and TSH stand for?

A

TRH - thyrotropin releasing hormone

TSH - thyroid stimulating hormone

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9
Q

What are the main examples of autoimmune thyroiditis?

A

Hashimoto’s thyroiditis (hypofunction)

Grave’s disease (hyperfunction)

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10
Q

What are the common features of autoimmune thyroiditis?

A

Increased incidence in family members
Susceptibility associated with the HLA haplotype
Association with other autoimmune diseases

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11
Q

What are non-immune related causes of inflammation of the thyroid?

A 
Palpation
Subacute lymphocytic
De Quervain's 
Infection
Riedel's
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12
Q

What is thyrotoxicosis?

A

When symptoms and signs occur as a result of excess T3 and T4

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13
Q

What are the causes of thyrotoxicosis?

A 
Hyperthyroidism
Hyperfunctioning nodules and tumours
TSH secreting pituitary adenomas
Thyroiditis
Ectopic production
Facticious
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14
Q

What is Grave’s disease?

A

An autoimmune disorder of thyroid gland hyperactivity

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15
Q

Who are commonly affected by Grave’s disease?

A

Women (10 times more than men)

20-40 years old

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16
Q

What is the action of anti-TSH receptor antibodies?

A

Act to stimulate receptors and mimic the effect of TSH

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17
Q

What are the anti-TSH receptor antibodies?

A

Thyroid stimulating immunoglobulin
Thyroid growth stimulating immunoglobulin
TSH binding inhibitor immunoglobulin

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18
Q

What triad of features are classic of Grave’s disease?

A

Diffuse enlargement of the thyroid
Eye changes (exophthalmus)
Pretibial myxoedema

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19
Q

Which histological changes occur in Grave’s disease?

A

Most follicles contain little or no thyroglobulin, and where there is thyroglobulin, there aren areas of pallor at the edges
In between follicles is abundant lymphocyte invasion

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20
Q

What is hypothyroidism?

A

Symptoms and signs due to low levels of T3 and T4

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21
Q

What are the causes of hypothyroidism?

A 
Hashimoto's thyroiditis (autoimmune)
Iodine deficiency
Drugs (e.g. lithium)
Post-therapy (surgery, irradiation)
Congenital abnormalities
Born errors of metabolism
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22
Q

What are secondary and tertiary hypothyroidism?

A

A result of pituitary or hypothalamus pathology respectively

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23
Q

What is Hashimoto’s thyroiditis?

A

Gradual failure of thyroid function?

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24
Q

Who commonly present with Hashimoto’s thyroiditis?

A

Women (10-20 times more than men)

45-60 years old

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25
Q

Which antibodies are associated with Hashimoto’s thyroiditis?

A

Anti-thyroid antibodies (anti-thyroglobulin and anti-peroxidase)

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26
Q

What is the pathogenesis of Hashimoto’s thyroiditis?

A

CD8+ cells cause destruction of thyroid epithelium
Cytokines recruit macrophages that damage thyroid follicles
Thyroid follicles atrophy
Progressive fibrosis

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27
Q

What histological features can be seen in Hashimoto’s thyroiditis?

A

Prominent lymphoid infiltration
Lymphoid follicles with reactive appearing germinal centres
Islands of residual normal thyroid follicles containing thyroglobulin

28
Q

What may precede hypothyroidism?

A

Transient hyperfunction (Hashitoxicosis)

29
Q

What is there an increased risk of in Hashimoto’s thyroiditis?

A

B cell non-Hodgekin’s lymphoma

30
Q

What is a goitre?

A

Any enlargement of the thyroid gland

31
Q

What are goitres usually caused by?

A

Lack of dietary iodine

Lack of bioavailability of iodine

32
Q

How does a goitre form?

A

Reduced T3/T4 production causes rise in TSH, stimulating gland enlargement

33
Q

Who commonly present with diffuse goitres?

A

Women

Puberty-aged and young adults

34
Q

What will thyroid hormone levels be like in a diffuse goitre?

A

T3 and T4 usually normal

TSH often high or upper limit of normal

35
Q

What are the different types of goitre?

A

Diffuse

Multi-nodular

36
Q

What is a multi-nodular goitre?

A

One that has evolved from a long-standing simple goitre due to recurrent hyperplasia and involution

37
Q

What effects can a large multi-nodular goitre cause?

A

Airway obstruction
Dysphagia
Compression of vessels

38
Q

What are the thyroid neoplasms?

A 
Follicular adenoma
Papillary carcinoma
Follicular carcinoma
Medullary carcinoma
Anaplastic carcinoma
39
Q

What is the description of a follicular adenoma?

A

Discrete solitary mass

40
Q

What are the symptoms of a follicular adenoma?

A

Usually asymptomatic and incidental finding

Local symptoms e.g. dysphagia if large

41
Q

What is the pathology of a follicular adenoma?

A

Encapsulated by a surrounding collagen cuff
Composed of neoplastic thyroid follicles
Usually non-function but can secrete thyroid hormones

42
Q

What are follicular adenoma usually caused by?

A

Mutations of the TSHR signalling pathway

43
Q

What is themes common thyroid carcinoma?

A

Papillary carcinoma

44
Q

What are the causes of thyroid carcinomas?

A 
Ionising radiation (papillary carcinoma)
Iodine deficiency (follicular carcinoma)
MEN2 (medullary carcinoma)
45
Q

Describe the pathology of papillary carcinomas

A

Usually a solitary nodule in the thyroid, can be multifactorial, often cystic, may be calcified

46
Q

What are the symptoms and signs of papillary carcinomas?

A 
Lesion in the thyroid gland or cervical lymph node mass
Hoarseness
Dysphagia
Cough
Dysphnoea
47
Q

How do papillary carcinomas spread?

A

Lymph node metastasis

Uncommonly haematogenous spread, usually to lung

48
Q

What is the prognosis for papillary carcinomas?

A

Good - survival at 10 years is 95%+

Prognosis worse as age increases, if there is extra-thyroid extension or if distant metastases

49
Q

Who commonly present with follicular carcinomas?

A

Women

40s and 50s

50
Q

Describe the pathology of follicular carcinomas

A

Usually a single nodule

Slowly enlarging, painless, non-functional

51
Q

What is the spread of follicular carcinomas?

A

Rarely lymphatic spread

Can have haematogenous spread to bone, lungs, liver

52
Q

Do follicular carcinomas commonly spread locally?

A

Yes - can be widely or minimally invasive

53
Q

What are features of a widely invasive follicular carcinoma?

A

More solid architechture
Less follicular architecture
More mitotic activity

54
Q

What are the features of a minimally invasive follicular carcinoma?

A

Follicular architecture (well differentiated)
May have part surrounding capsule
Difficult to distinguish from adenoma

55
Q

What is the prognosis of follicular carcinomas?

A

Depends on extent of invasion and stage at presentation
If high stage - 50% mortality at 10 years
If minimally invasive - >90% survival at 10 years

56
Q

What do medullary thyroid carcinomas derive from?

A

C cells

57
Q

What are the types of medullary thyroid carcinomas?

A

Sporadic (70%)
Associated with multiple endocrine neoplasia (MEN2a or 2b)
Familial medullary carcinoma

58
Q

Who usually presents with medullary thyroid carcinomas?

A

Can be very young if associated with MEN

Adults in 40s and 50s

59
Q

What is the difference between sporadic and familial medullary thyroid carcinomas?

A

Sporadic - solitary nodules

Familial - bilateral or multicentric

60
Q

Describe the pathology of medullary thyroid carcinomas?

A

Composed of spindle or polygonal cells arranged in nests, trabeculae or follicles

61
Q

How do medullary thyroid carcinomas present?

A 
Neck mass with local effects (dysphagia, hoarseness, airway compromise)
Paraneoplastic syndrome (diarrhoea, Cushing's)
62
Q

What is the treatment for medullary thyroid carcinomas?

A

Total thyroidectomy

63
Q

What is the prognosis for medullary thyroid carcinomas?

A

5 and 10 year survival overall about 80% and 73%

35% recurrence in patients who get a total thyroidectomy

64
Q

What are the good and poor prognostic factors for medullary thyroid carcinomas?

A

Good: young age, female, small tumour size, confined to thyroid with no meastases
Poor: necrosis, many mitosis, squamous metaplasia, MEN2b

65
Q

What are anapaestic carcinomas?

A

Undifferentiated and aggressive tumours
Usually present in older patients
Can occur in patients with history of differentiated thyroid carcinoma
Rapid growth and involvement of neck structures

Y2 - Endocrine (9 decks)

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