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Endocrine SB > Thyroid > Flashcards

Thyroid Flashcards

1
Q

what does the thyroid secrete

A

Thyroxine (T4)
Tri-iodothyronine (T3)
Calcitonin

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2
Q

what does the parathyroid secrete

A

PTH

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3
Q

what cells secrete calcitonin

A

Parafollicular C cells

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4
Q

steps of synthesis and storage of T3 and T4

A

1 - Iodine taken up by follicle cells
2 - iodine attached to tyrosine residues on thyroglobulin to form (MIT) & (DIT)
3 - coupling of MIT+ DIT = T3
and DIT + DIT = T4
4 - stored in COLLOID thyroglobulin till required

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5
Q

how many iodine units does DIT and MIT contain

A

DIT - 2

MIT - 1

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6
Q

what does CARBIMAZOLE & PROPYLTHIOURACIL inhibit

A

Iodine attaching to tyrosine

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7
Q

what is the major biologically active thyroid hormone

A

T3

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8
Q

what thyroid hormone is produced the most by the thyroid

A

T4 - thyroxine

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9
Q

where is T4 converted to T3

A

liver and kidney

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10
Q

what triggers the release of T3 and T4

A

the TSH from the pituitary gland

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11
Q

what form of T3/T4 is the biologically active form

A

unbound/free

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12
Q

what are the plasma protein binding molecules of T3/T4

A

Thyroxine binding globulin (TBG – approx 70%)
Thyroxine binding prealbumin (TBPA- approx 20%)
Albumin

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13
Q

Metabolic state correlates LESS closely with the free than with the total concentration in the plasma - true or false

A

False

Correlates MORE with free/unbound concentration

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14
Q

is thyroid hormone important for growth ?

A

yes

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15
Q

what is needed to treat symptoms in initial stages on therapy for hyperthyroidism

A

Beta blocker e.g. Propranolol

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16
Q

what stimulates the release of TSH from the ANTERIOR pituitary

A

TRH from the hypothalamus

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17
Q

what can inhibit TRH and TSH release

A

stress

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18
Q

what type of rhythm does thyroid hormone release have

A

circadian rhythm

- highest late at night, lowest AM

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19
Q

severe complication of hypothyroidism

A

adults - myxoedema (puffy face/hands/feet)

babies - cretinism (dwarfism and limited mental function)

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20
Q

when would there be a lingual thyroid

A

failure of descent - embryological abnormality

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21
Q

where can the thyroid be found if there has been excessive descent

A

retrosternal in mediastinum

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22
Q

where does the thyroid descend from

A

foramen caecum

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23
Q

what is the thyroid composed of

A

follicles

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24
Q

what is each follicle surrounded by

A

cuboidal follicular epithelial cells.

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25
Q

what is in the centre of follicle cells

A

thyroglobulin - dense amorphic pink material

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26
Q

pathway of release of T3 and T4

A
  • TSH binds to TSH receptor
  • G proteins activated
  • GTP to GDP
  • production of cAMP
  • increased production and release of T3 and T4
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27
Q

what are the antibodies of Grave’s Disease

A

Anti TSH receptor antibodies

  • Thyroid stimulating immunoglobulin (most specific for Graves)
  • Thyroid growth stimulating immunoglobulin
  • TSH binding inhibitor immunoglobulins
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28
Q

what is the triad of features associated with Graves

A
  • Hyperthyroidism with diffuse enlargement of the thyroid
  • Eye changes (exophthalmos)
  • Pretibial myxoedema.
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29
Q

why is there eye changes in Graves disease

A

fibroblasts (etc.) in the eye expressing TSH receptors

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30
Q

what antibodies are associated with Hashimotos’ thyroiditis

A

Anti-thyroid antibodies

  • Anti-thyroglobulin
  • anti-peroxidase
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31
Q

what is Hashimoto’s associated with

A

Middle aged women
Other Autoimmune disease
HLA – DR3 and DR5

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32
Q

what causes the destruction of the thyroid in Hashimoto’s

A

CD8 +ve cells - cytotoxic destruction

cytokine mediated cell death

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33
Q

what polymorphisms in what genes are associated with Hashimoto’s

A

CTLA-4
- polymorphisms increase risk of auto-immune diseases

PTPN -22
- inhibits T cell function

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34
Q

what may precede Hashimoto’s

A

Transient hyperfunction (Hashitoxicosis)

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35
Q

what is a goitre

A

any enlargement of the thyroid gland

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36
Q

what commonly causes multi nodular goitre

A

lack of dietary iodine

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37
Q

what does a lack of iodine cause

A

cannot produce T3 and T4; causes thyroid to work harder resulting in increase in size due to rise in TSH

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38
Q

what does diffuse goitre normal present with

A

mess effect i.e. neck lump

T3/T4 normal so euthyroid even if TSH is high

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39
Q

how can multi-nodular goitre develop

A

evolution from long standing simple goitre i.e. recurrent hyperplasia

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40
Q

what is the pathology seen in multi-nodular goitre

A

Rupture of follicles, haemorrhage, scarring, calcification

41
Q

what are the benign neoplasms of the thyroid

A

Follicular adenoma

42
Q

what are the malignant neoplasms of the thyroid (most to least common)

A
  • papillary
  • follicular
  • medullary
  • anaplastic
43
Q

pathology of adenoma

A

Discrete solitary mass

  • incidental finding normally
  • can cause local symptoms

Encapsulated by collagen cuff

Composed of neoplastic thyroid follicles

44
Q

features of adenoma

A

normally non- functional

can secrete thyroid hormones - thyrotoxicosis

45
Q

what mutations are commonly seen in adenomas

A

TSHR signalling pathway

46
Q

what are most malignant thyroid cancers derived from

A

follicular epithelium

47
Q

Pathology of papillary carcinoma

A

usually solitary nodule in thyroid (can be multi)
Cystic
Calcified; psammoma body

48
Q

survival rates for papillary carcinoma

A

good - 10 yrs 95%+

49
Q

what can be the local effects of a cancer in the thyroid

A

hoarseness
dysphadia
cough
dyspnoea

50
Q

pathology of Follicular carcinoma

A

Usually single nodule

  • Slowly enlarging, painless, non-functional
  • often haematogenous spread
  • more likely to invade other areas
51
Q

prognosis of follicular carcinoma

A

Depends on Extent of invasion and stage at presentation

50% mortality at 10yrs

52
Q

pathology of Medullary Thyroid Carcinoma (MTC)

A

Derived from C-Cells (neuroendocrine)
- Can secrete calcitonin

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

Sporadic cases - solitary nodule
Familial cases - bilateral

53
Q

what is MTC associated with

A

MEN IIA or IIB

Familial medullary carcinoma

54
Q

features of anaplastic carcinomas

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

55
Q

what is the parathyroid composed on

A

chief cells

56
Q

what are the actions of chief cells

A

secrete PTH

act on Ca homeostasis

57
Q

what supports the chief cells

A

oxyphil cells

58
Q

what is the most common cause of hyperparathyroidism

A

small adenomas

59
Q

what is hyperplasia of the parathyroid gland associated with

A

MEN I and MEN IIa

60
Q

what leads to secondary hyperparathyroidism and what can cause this

A

Chronic hypocalcaemia causes compensatory over activity of the parathyroid glands

e.g. renal failure, Vit D deficiency

61
Q

what is Tertiary hyoerparathyroidism associated with

A

hypercalcaemia

62
Q

what does hyperparathyroidism cause

A

hypercalcaemia

63
Q

what are the symptoms of hyperparathyroidism

A

STONES
- gall stones, renal stones

MOANS
- depression, lethargy, seizures

GROANS
- Constipation, nausea, peptic ulcer disease, pancreatitis,

BONES
- pain, fracture, osteoporosis

64
Q

when can hypoparathyroidism happen

A

Post-op

Di George syndrome

65
Q

what are the surgical options of the treatment of thyroid

A

Thyroid lobectomy with isthmusectomy
Sub-total thyroidectomy
Total thyroidectomy

66
Q

what is papillary thyroid cancer associated with

A

Hashimoto’s thyroiditis

67
Q

where does thyroid cancer spread to

A

lungs, bones, liver, brain
via lymphatics
(via haematogenously for Follicular carcinoma)

68
Q

Ix of suspected thyroid cancer

A

1st - US guided FNA of lesion

2nd - excision biopsy of lymph node

69
Q

what is not useful Ix for thyroid cancer

A

CT/MRI

Isotope thyroid scan

70
Q

what are clinical predictors of malignancy

A 
New thyroid nodule age 50
Male
Nodule increasing in size
lesion > 4cm in diameter
History of head and neck irradiation
Vocal cord palsy
71
Q

what is Tx for thyroid cancer

A

surgery

72
Q

what system is used to identify if patient is high or low risk in thyroid cancer

A

AMES system

A - age
M - mets
E - extend of primary tumour
S - size of primary tumour

73
Q

when is sub-total or total thyroidectomy done

A
  • DTC with extra-thyroidal spread
  • Bilateral / multifocal DTC
  • DTC with distant metastases
  • DTC with nodal involvement
  • Patients in AMES high risk group
74
Q

what type of thyroid cancer had a higher percentage of lymph node spread

A

Papillary

75
Q

what is checked and monitored after thyroid removal

A

calcium levels

76
Q

Tx post op

A

T3 or T4

77
Q

when is whole body iodine scanning used

A

in patients who have undergone sub-total or total thyroidectomy

78
Q

what is administered in thyroid remnant ablation

A

I - 131

79
Q

in primary hyperthyroidism what are the TFT results

A

TSH low

T4/T3 high

80
Q

in primary hypothyroidism what are the TFT results

A

TSH high

T4/T3 low

81
Q

in secondary hypothyroidism what are the TFT results

A

TSH low

T4/T3 low

82
Q

what can cause secondary hypothyroidism

A

pituitary gland failure

83
Q

in secondary hyperthyroidism what are the TFT results

A

TSH high

T4/T3 high

84
Q

what can severe hypothyroidism cause

A

myxoedema coma

85
Q

what organs can play a part in secondary hypothyroidism

A

hypothalamus

pituitary

86
Q

what antibody is linked to Hashimoto’s

A

Thyroid Peroxidase Antibodies

87
Q

what blood condition is common in hypothyroidism

A

Macrocytosis - enlarged RBC

88
Q

why is hyponatraemia seen in hypothyroidism

A

reduced renal tubular water loss

89
Q

why is hyperprolactinaemia seen in hypothyroidism

A

↑TRH leads to ↑ prolactin secretion

90
Q

what is Mx for hypothyroid

A

Thyroxine (T4)
50-100 in younger patients
25-50 in elderly

91
Q

what measurement is used as an index of therapeutic success and potential toxicity in primary hypothyroidism

A

TSH levels

92
Q

when is T4 used to monitor treatment in hypothyroid

A

in secondary hypothyroidism

93
Q

Tx for hyperthyroidism

A

Carbimazole

Propylthiouracil

94
Q

when would Propylthiouracil be used over Carbimazole

A

in pregnancy

95
Q

what are the precautions in radio-iodine

A 
Avoid close prolonged contact with young children/pregnant women
Don’t share a bed for x days
Avoid Pregnancy for 6 months
Ensure not Pregnant
High Risk of Hypothyroidism
96
Q

what are risks in removing thyroid through surgery

A

Scar
Risk to recurrent laryngeal nerve palsy
Hypothyroidism
Hypo-parathyroidism

97
Q

what type of hyperthyroidism can be triggered by a virus

A

De Quervains

Sub-Acute Thyroiditis

98
Q

what antiarrhythmic agent can cause thyroid dysfunction

A

Amiodarone

99
Q

if there is subclinical thyroid disease where will the abnormality in results be

A

TSH

T4/3 will be normal

Endocrine SB (15 decks)

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