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Endocrinology > Thyroid Tutorials > Flashcards

Thyroid Tutorials Flashcards

1
Q

what are thyroid follicles

A

balls of epithelial cells surrounding proteinaceous (non cellular) colloid

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2
Q

where are thyroid hormones stored

A

in colloid

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3
Q

how is T3 produced

A

de-iodination of T4 within target cells outside the thyroid

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4
Q

what do thyroid hormones bind to

A

serum proteins- thyroid binding globulin

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5
Q

what enzyme activates iodine

A

a peroxidase enzyme

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6
Q

how is tyrosine involved in thyroid hormones

A

tyrosine residues on thyroglobulin are iodinated forming MIT and DIT which couple together to form T4 and T3

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7
Q

what is thyroglobulin

A

protein made by thyroid cells

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8
Q

how are thyroid hormones secreted

A

colloid is resorbed into the thryoid cells by endocytosis
thyroglobulin is broken down by lysosomes to release (T4 and some T3)
secreted into blood stream

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9
Q

what stimulated the thyroid to produce thyroid hormones

A

TSH secreted by the pituitary

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10
Q

what is thyrotropin

A

thyroid stimulating hormone

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11
Q

what are the types of goitre

A

diffuse and nodular

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12
Q

what are the 7 causes of goitres

A 
iodine deficiency
multinodular goitre 
graves disease 
thyroiditis 
tumour 
cysts
inherited (abnormality of enzyme pathway or T4 receptor)
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13
Q

what can cause thyroiditis

A 
(thyroiditis is an inflammatory response)
hashimotos (autoimmune) 
subacute causes (de Quervains, viral) 
acute causes (bacterial) 
drugs (lithium, amiodarone)
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14
Q

what are the usual features of a malignant thryoid nodule

A 
<20 and >70 years old
male 
dysphagia/ dysphonia 
previous neck irradiation 
firm, hard, immobile 
cervical lymphadenopathy
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15
Q

what are usual features of a benign thyroid nodules

A 
FHX of autoimmune diseases
FHX benign nodules/ goitre 
associated hormone disturbances 
pain/ tenderness 
soft, smooth, mobile
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16
Q

how should thyroid lumps over 1.5 cm be investigated

A

ultrasound and fine needle aspirate (under ultrasound guidance)

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17
Q

what is a thyroid isotope scan useful for

A

establishing the cause of thyrotoxicosis- can identify multinodular goitres, toxic adenomas and thyroiditis

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18
Q

what antibodies can you check for in thyroid disease

A

anti TPO (thyroid peroxidase)
anti-thyroglobulin
TSH receptor antibody (TRAB)

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19
Q

what do thyroid function tests show in primary hypothyroidism

A

increased TSH

decreased T4/T3

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20
Q

what do thyroid function tests show in secondary hypothyroidism

A

decreased TSH

decreased T4/3

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21
Q

what do thyroid function tests show in hyperthyroidism

A

decreased TSH

increased T4/3

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22
Q

what do thyroid function tests show in subclinical hyperthryoidism

A

decreased TSH

normal T3/4

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23
Q

what do thyroid function tests show in sick euthyroid

A

normal or decreased TSH

decreased T4/3

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24
Q

what are the symptoms of hyperthyroidism

A 
nervous, anxious, irritable 
warm, sweaty, heat intolerance
tachycardia, palpitations,
weight loss, increased appetite (10% have weight gain),
diarrhoea,
amenorrhoea,
weakness, fatigue
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25
Q

what are the causes of hyperthyroidism

A 
autoimmune (graves) 
multinodular goitre 
toxic solitary nodule 
thyroiditis 
exogenous thyroid hormones 
thyroid cancer 
hydatiform mole 
TSH secreting pituitary tumour
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26
Q

what is a thyroid storm

A

CRISIS
untreated/ inadequately treated thyrotoxicosis + preciptating factors (MI, infection, PE)
rare but life threatening - medical emergency

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27
Q

what are the features of a thryoid storm

A 
HR increased 
BP decreased 
fever
altered mental status 
multiorgan failure
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28
Q

how do you manage a thyroid crisis

A 
carbimazole (high dose)
beta blockers 
hydrocortisone 
potassium iodide 
IV fluids +/- inotropes 
treat precipitating cause (MI, infection, PE)
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29
Q

what are the signs associated with graves

A

dysthyroid eye disease
thryoid acropathy
pretibial myxoedema

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30
Q

what are the forms of dysthyroid eye disease

A

swelling of extra ocular muscles, lymphocytic infiltration, late fibrosis and muscle tethering.

causes:
- proptosis (eye protusion)
- lid lag
- opthalmoplegia (swelling of muscles causing orbital muscle paralysis - can present as diplopia)

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31
Q

describe thyroid acropachy

A

oft tissue swelling and periostial bone changes

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32
Q

what can worsen graves opthalmology

A

smoking and hypothyroidism

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33
Q

what are the clinical features of dysthyroid eye disease

A 
grittiness, watery eyes, conjunctival injection,
eyelid retraction,
proptosis,
visual blurring,
painful eye movements
34
Q

what are the primary causes of hypothyroidism

A

autoimmune- hasimotos/ postpartum

iatrogenic- post surgery or radioiodine

other- excess iodine, iodine deficiency and goitrogens (lithium etc.), inborn errors of thyroid hormone synthesis

35
Q

what are the secondary causes of hypothyroidism

A

pituitary or hypothalamic disease

36
Q

what other than primary and secondary causes of hypothyoridism can cause hypothyroidism

A

peripheral resistance to thyroid hormone

37
Q

what is the treatment for hypothyroidism

A

levothyroxine (T4)
- start at 50 or 200 micrograms (lower if IHD or LVF)

liothyronine (T3)
-start at 20 micrograms

38
Q

what are the symptoms of hypothyroidism

A 
fatigue 
lethargy
cold intolerance 
weight gain 
dry puffy skin 
hair loss 
constipation 
menorrhagia 
muscle weakness
bradycardia
39
Q

what is the ultrasound classification for ultrasound thryoid cancers

A

U1-2 benign
U3- indeterminate
U4-5 malignant

40
Q

what are 80% of all thyroid cancers

A

papillary cell carcinomas

41
Q

what would been seen in thyroid tests for a goitre caused by menopause

A

suppressed TSH and raised T4

42
Q

what is pemburtons sign

A

used to evaluate venous obstruction in patients with goiters. The sign is positive when bilateral arm elevation causes facial plethora

43
Q

why do anti thyroid drugs take 3-4 weeks minimum to work

A

as stores of thyroid hormones

44
Q

what should you be careful of when on antithyroid drugs

A

agranulocytosis- suppression of bone marrow, be aware of any sore throat or mouth ulcers

45
Q

what changes should be made in thyrotoxicosis during pregnancy

A

switch carbimazole to propylthiouracil for first trimester then back in second
thyrotoxicosis very bad for feotus, make sure its well controlled

46
Q

if a patient is non compliant to thyrotoxicosis meds what are their treatment options

A

radio iodine, sugery

47
Q

what will probably happen eventually after radio iodine

A

will develop hypothyroidism, be on lifelong thyroxine

48
Q

what antibodies for hypothryoidism

A

Anti-thyroid peroxidase (anti-TPO) antibodies or anti-thyroglobulin antibodies are found in 90-95% of patients with autoimmune thyroiditis

49
Q

what antibodies for hyperthyroidism

A

Antimicrosomal antibodies - against thyroid peroxidase. Thyroid peroxidase antibodies are present in about 75% of cases of Graves

Antithyroglobulin antibodies

TSH-receptor antibodies (very specific and sensitive for graves)

50
Q

what is the most common cause of hypopituitarism

A

a pituitary tumour

51
Q

why does the thyroid move on swallowing

A

as it is attached to the upper end of the trachea

52
Q

what cell types make up the thyroid

A

follicular cells (encase colloid) and parafollicular cells (lie within connective tissue)

53
Q

what cell type produces thyroglobulin

A

follicular

54
Q

what cell type produces calcitonin

A

parafollicular C cells

55
Q

where is thyroglobulin stored

A

in the colloid

56
Q

what is pinocytosis

A

occurs at colloid, causes the release of thyroglobulin

57
Q

what acts on thyroglobulin to make thyroid hormones

A

lysosomes

58
Q

how is iodine involved in thyroid hormones

A

enters from bloodstream in follicles
attached to the tyrosine residues on thyroglobulin to form MIT and DIT
T3= 2 x MIT
T4= MIT + DIT

59
Q

where are T3 and T4 stored

A

in colloid thyroglobulin

60
Q

what is the majority of secreted thyroid hormone

A

T4 (triiodothyronine)

61
Q

where is T4 converted to T3

A

liver and kidneys

62
Q

are T3 and T4 hydrophilic or phobic

A

phobic

calcitonin is phillic

63
Q

what effects does thyroid hormone have on metabolism

A

increases protein synthesis, glucose and fatty acid plasma levels, thermogenesis, bone turnover and gut motility

64
Q

what effect does growth hormone have on fat tissues

A

increases lipolysis, increasing plasma fatty acids

65
Q

what effect does growth hormone have on the liver

A

increases gluconeogenesis, increasing plasma glucose

66
Q

what effect does growth hormone have on muscle

A

increases protein synthesis, decreasing plasma amino acids

67
Q

how does thyroid hormone affect fat storage

A

decreases it

68
Q

what is the role of thyroid hormone in the nervous system

A

increase responsiveness to neurotransmitters - increases the numbers of receptors to these transmitters (e.g. adrenaline and noradrenaline)

69
Q

what regulates thyroid hormone

A

TRH (from hypothalamus, acts on ant pituitary) and TSH (ant pituitary, acts on thyroid gland) positive feedback

T3 negatibe feedback on ant pituitary and hypothalamus

70
Q

what hormone will always be raised in graves

A

T4 (T3 may be high or normal)

71
Q

what complications are specific to graves disease

A

exopthalamus- loss of eye movement, feels gritty, eye pushed forward, blurred vision, eye redness (1-2 years after diagnosis)

pretibial myxoedema- bilateral plaque formation on the anterior surface of lower legs, orange fell look, non pitting, 1-2 years after diagnosis

72
Q

what causes exopthalamus

A

receptors in tissue and muscle surrounding the eye respond to TSI- causes water build up and retro-orbital swelling

collagen fibres may also be deposited which leads to loss of function and lack of movement

73
Q

what is lid lag

A

delay of the upper eyelid on downward rotation of the eye

74
Q

what hormone is predominantly secreted by thyroid adenoma and carcinomas

A

T3

75
Q

what is de Quervains thyroiditis

A

acute inflammatory process usually due to viral that causes hyperthyroidisim along with fever, malaise, local tenderness of the thyroid
after a few will will transition into transient hypothyroidism the euthyroid

76
Q

do you get goitres in iodine deficiency hypothyroidism

A

usually yes

77
Q

what do antibodies attach in hashimotos

A

thyroid peroxidase (enzyme in production of thyroid hormones) and thyroglobulin

78
Q

what are the secondary causes of hypothyroidism

A

deficiency or loss of function of the hypothalamus or pituitary: infiltration, infection or malignancy

79
Q

what causes decreased TSH with normal T4 and T3

A

subclinical hyperthyroidism

80
Q

what causes decreased TSH with decreased T4 and T3

A

pituitary disease

81
Q

how are anti thyroid drugs dosed

A

start with high dose then reduce over 12-18 months

82
Q

is agranulocytosis carbimazole or PTU

A

carbimazole

Endocrinology (46 decks)

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