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03- Endocrine > Thyroid > Flashcards

Thyroid Flashcards

1
Q

descirbe primary thyroid disease

A

disease affecting thyroid gland itself

autoimmune thyroid disease most common

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2
Q

describe scondary thyroid disease

A

hypothalmic or pituitary disease

no thyroid gland pathology

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3
Q

what is TSH

A

thyroid stimulating hormone

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4
Q

where is TSH released?

A

thyrotroph cells in anterior pituitary

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5
Q

TSH is released in response to what?

A

thyrotropin releasing hormone TRH

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6
Q

TSH is also called what?

A

thyrotropin

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7
Q

release of TSH results in what?

A

production of T3 and T4

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8
Q

99% of T4 and T3 is bound to what?

A

plasma proteins

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9
Q

what plasma proteins do T3 and T4 bind to?

A

Thyroxine Binding Globulin (TBG)- 70%

Transthyretin (TTR)- 20%

Albumin- 5%

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10
Q

what levels of free T3/4 and TSH would be seeen in primary hypothyroidism

A

free T3/4 low

TSH high

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11
Q

what levels of T3/4 and TSH would be seen in primary hyperthyroidism?

A

free T3/4 high

TSH low

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12
Q

what si the difference between primary and secondary thyroid disease?

A

primary- problem with thyroid gland iself

secondary- problem with hypothalmus/pituitary

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13
Q

what levels of T3/4 and TSH would be seen in secondary hypothyroidism?

A

low free T3/4

TSH low (or normal)

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14
Q

what levels of free T3/4 and TSH would be seen in secondary hyperthyroidism?

A

free T3/4 high

TSH high (or normal)

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15
Q

define myxoedema

A

severe hypothyroidism

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16
Q

pretibial myxoedema is a rare clinical sign in which autoimmune thyroid condition?

A

Graves disease

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17
Q

graves disease results in hypo/hyperthyroidism?

A

hyperthyroidism

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18
Q

what are soem goitrous causes of hypothyroidism?

A

hashimotos thyroiditis

iodine deficiency

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19
Q

what are some non-goitrous causes of hypothyroidism?

A

atrophic thyroiditis

post radiotherapy

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20
Q

what would be a self-limiting cause of hyperthyroidism?

A

withdrawl of antithyroid drugs

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21
Q

describe hashimotos thyroiditis?

A

autoimmune destruction of thyroid gland and reduced thyroid hormone productioin

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22
Q

hashimotos is characterised by which antibodies?

A

antibodies against thyroid peroxidase (TPO)

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23
Q

what is seen microscopically in hashimotos?

A

T cell infiltrate

inflammation

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24
Q

what is prescribed to people with hypothyroidism?

A

levothyroxine

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25
Q

how soon should TSH levels be checked once started on thyroxine in hypothyroidism?

A

2 months after any dose change

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26
Q

once established how often should TSH be checked?

A

12-18 months

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27
Q

when should levothyroxine be taken to try and prevent problems with absorption?

A

before eating

before any other medications

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28
Q

what is thyrotoxixosis?

A

the state when you have too much thyroxine

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29
Q

what is hyperthyroidism?

A

condition where you get thyrotoxic due to thyroid gland pathology

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30
Q

how cna graves disease affect your bones?

A

osteoporosis

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31
Q

over 90% of people with Graves will have detectable levels of which antibody?

A

TRAb- TSH receptor antobody

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32
Q

severe hyperthyroidism is referred to as what?

A

thyroid storm

33
Q

thyroid storm is common in those with which autoimmune condition?

A

graves

34
Q

what is the treatment of hyperthyroidism?

A

antithyroid drugs

35
Q

how do antithyroid drugs work?

A

inhibit TPO therby blocking thyroid hormone synthesis

36
Q

what is the first line antithyroid drug used in hyperthyroidism?

A

carbimazole

37
Q

what is a side effect of antithyroid drugs?

A

agranulocytosis

38
Q

when is the risk of angranulocytosis greatest when prescribed an antithyroid drug?

A

first 6 weeks

39
Q

which B blocker is commonly used in hyperthyroidism?

A

propanolol

40
Q

in which group of patients is the use of radioiodine contraindicated in hyperthyroidism?

A

contraindicated in pregnancy

41
Q

what are the risks with surgery in hyperthyroidism?

A

recurrent laryngeal nerve palsy

hypothyroidism

hypoparathyroidism

42
Q

what is thyroiditis?

A

inflammation of thyroid

43
Q

what is non-thyroidal illness also known as?

A

sick euthyroid syndrome

44
Q

what does non-thyroidal illness refer to?

A

impact of illness e.g severe infection- TSH supressed then rises again with recovery

45
Q

thyroid gland tissue secretes what?

A

thyroxine T4

tri-iodothyronine T3

calcitonin

46
Q

which imaging technique is particulary useful when investigating the thyroid?

A

iodine uptake scan

47
Q

an iodine uptake scan will appear darker in hypo/hyper thyroidism?

A

hyperthyroidism

48
Q

which cells secrete calcitonin?

A

parafollicular C cells

49
Q

what is required for the synthesis of thyroid hormones?

A

iodine

50
Q

iodine is taken up by which thyroid cells?

A

follicle cells

51
Q

iodine attaches to what in order to form MIT and DIT?

A

iodine attaches to tyrosine residues on thyroglobulin

52
Q

coupling of MIT + DIT forms what thyroid hormone?

A

T3

53
Q

coupling of 2 DIT forms what?

A

T4

54
Q

T3 and T4 are stored where?

A

colloid thyroglobulin

55
Q

how long can T3 and T4 be stored for?

A

weeks to months

56
Q

which thyroid hormone is the most abundant?

A

T4

57
Q

which thyroid hormone is the most biologically active?

A

T3

58
Q

which form of thyroid hormone is biologically active bound/unbound?

A

unbound

59
Q

T3 acts on what kind of receptor?

A

nuclear receptor

60
Q

why do T3 and T4 bind to plasma proteins?

A

hydrophobic

lipophilic

61
Q

metabolic state correlates more with the free T3 and T4/ the total conc in plasma?

A

the free T3 and T4

62
Q

thyroid hormones target virtually every tissue to alter what two things?

A

gene transcription

protein synthesis

63
Q

what are the physiological effect sof thyroid hormones?

A

metabolism

growth & development

reproduction

behaviour

64
Q

thyroid hormones inc/dec basal metabolic rate

A

increase metabolic rate

65
Q

how do thyroid hormones increase metabolic rate?

A

inc no & size metabolic rate

inc oxygen use and rates of ATP hydrolysis

66
Q

thyroid hormones inc/dec thermogenesis?

A

incerease thermogenesis

67
Q

what percentage of temperature regulation is due toi thyroif hormones?

A

30%

68
Q

what are the metabolic effects of thyroid hormones?

A

inc blood glucose

inc fatty oxid in tissues

inc protein synthesis

69
Q

whoch growth hormone requires thyroid hormones?

A

Growth Hormone Releasing Hormone (GHRH)

70
Q

describe permissive sympathomimetic action

A

thyroid hormones inc responsiveness to adrenaline and noradrenaline by increasing numbers of receptors

71
Q

T3 and T4 exert negative feecback on which hormones?

A

release of TRH and TSH

72
Q

what kind of receptor is TSH?

A

G protein coupled receptor

73
Q

what can alter thyroid hormone levels?

A

low temp in babies and chlidren

stress

circadian rhythm

74
Q

what enzyme is important in the activation and deactivation of thyroid hormone?

A

Deiodinase enzymes

75
Q

what does deiodinase enzyme do to thyroid hormone?

A

adds or removes an iodine atom from the outer ring

76
Q

what are the two inactive forms of thyroid hormone produced by deioinase enzyme?

A

rT3 (reverse T3) from T4

T2 from T3

77
Q

of the three subtypes od deiodinase enzyme which is the major determinant in the conversion of T4 to T3?

A

DII

78
Q

where are each of the deiodinase enzymes subtypes located?

A

DI- liver and kidneys

DII- heart, skeletal muscle, CNS, thyroid, pituitary

DIII- fetal tissue, placenta, brain

79
Q
A

03- Endocrine (9 decks)

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