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Endocrinology > Endo 5 - Hyperthyroid Disorders > Flashcards

Endo 5 - Hyperthyroid Disorders Flashcards

1
Q

State two common causes of hyperthyroidism?

A
  1. Grave’s Disease

2. Plummer’s Disease

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2
Q

What type of disease is Grave’’s disease?

A

Autoimmune

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3
Q

Describe the mechanism of Grave’s disease?

A

an autoimmune antibody which behaves like TSH and binds to the TSH receptor thus stimulating thyroid hormone production

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4
Q

What does the thyroid gland look like in Grave’s disease on a scan?

A

The thyroid gland is smoothly enlarged and the whole gland is active

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5
Q

What are some of the signs and symptoms in Grave’s disease?

A
  • rapid pulse
  • warm
  • localised pretibial myxoedema
  • exopthalmos
  • excitability/nervousness
  • loss of weight
  • oligomenorrhoea/ amenorrhoea
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6
Q

What are the two defining features of Grave’s disease?

A
  1. Localised pretibial myxoedema

2. Exopthalmos

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7
Q

Explain how pretibial myxoedema happens in Grave’s?

A

antibody mediated

non-pitting

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8
Q

What causes the exopthalmos?

A

another antibody, binds to muscles behind eye

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9
Q

What causes Plummer’s disease?

A

Benign adenoma in the thyroid gland

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10
Q

What would an iodine scan show in a patient with Plummer’s disease?

A

all the iodine will be taken up by the overactive tumourous part of the thyroid, so you see a hot nodule appear
the rest of the thyroid will not be seen as TSH is 0 so is not being stimulated

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11
Q

How does Plummer’s differ from Grave’s?

A

not autoimmune

so no pretibial myxoedema and no exopthalmos

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12
Q

Describe the effects of thyroxine on the sympathetic nervous system?

A

it sensitises beta adrenoceptors to basal levels of adrenaline and noradrenaline

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13
Q

So excess thyroxine causes…

A

symptoms of having high adrenaline

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14
Q

What causes lid lag?

A

High adrenaline

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15
Q

What is a thyroid storm?

A

medical emergency, a rare complication of hyperthyroidism

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16
Q

What are the features of a thyroid storm?

A
  • hyperpyrexia
  • accelerated tachycardia
  • cardiac failure
  • delirium
  • hepatic failure
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17
Q

What are the 4 treatments of hyperthyroidism?

A
  • Thionamides
  • Potassium iodide
  • radioiodine
  • beta blockers
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18
Q

Outline the physiology of iodine in the thyroid?

A
  • iodine taken up by the follicular cells
  • thyroperoxidase allows for iodination of tyrosine residues
  • allows for coupling of t1 and t2 to form t3 and t4
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19
Q

Describe the synthesis of thyroxine by follicular cells

A
  • thyroglobulin is a protein produced by follicular cells
  • iodine taken up by the follicular cells
  • thyroid peroxidase iodinates tyrosyl residues on the thyroglobulin to form t1 and t2 in the presence of hydrogen peroxide
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20
Q

What is the mechanism of action of thionamides?

A
  • inhibit thyroperoxidase so t3/t4 cannot be made

- reduced synthesis of thyroxine hromones

21
Q

Why do thionamides take around 2 weeks for their effects to be felt?

A

stores of thyroxine last 2 weeks + long half life

22
Q

What two diseases can thionamides be used to treat?

A

Plummer’s and Grave’s

23
Q

When do you use thionamide in a patient?

A

Use it before a thyroidectomy to stabilise the patient

24
Q

Why do you need to stabilise the patient before surgery?

A

cannot give anaesthesia to a hypertensive and tachycardiac patient

25
Q

Name 2 thionamides?

A

Carbimazole

Propylthiouracil

26
Q

What would you give a hyperthyroid patient while the thionamide takes two weeks to work?

A

non selective beta blockers

this will reduce the sensitisation of beta adrenoceptors to thyroxine

27
Q

What are some of the other added benefits of thionamides other than inhibiting thyroperoxidase?

A
  • suppress antibody production

- reduces deiodination of t4 to t3

28
Q

What are some of the unwanted effects of thionamides?

A
  • agranulocytosis
  • nausea
  • headaches
  • rashes
  • jaundice
  • joint pain
29
Q

Carbimazole is a pro drug, what does it get converted to to have its affect?

A

Methimazole

30
Q

Do thionamides cross the placenta?

A

Yes

31
Q

What should you do when prescribing thionamides to pregnant women/women looking to conceive?

A

Give as low dose as possible

32
Q

Which drug out of carbimazole and propylthiouracil crosses into the breast milk LESS?

A

PTU

33
Q

What is the mechanism of action of potassium iodide treatment?

A

massive dose of iodine can turn off the thyroid, inhibits the iodination of thyroglobulin and inhibits the production of hydrogen peroxide

34
Q

What is the Wolff-Chaikoff effect?

A

temporary reduction in thyroid hormones following ingestion of a huge amount of iodine

35
Q

Why is potassium iodide given before surgery?

A

reduces the size and vascularity of the thyroid gland

36
Q

Name 3 unwanted effects of potassium iodide?

A

rashes
fever
angioedema

37
Q

What is the form of potassium iodide given?

A

Lugol’s iodine

38
Q

What 3 things is Radioactive iodine 131 used to treat?

A

Grave’s disease
Plummers
Thyroid cancer

39
Q

What is the mechanism of action of radioactive iodine treatment?

A

Radioiodine taken up by the thyroid and accumulates in the colloid
emits beta particles in the colloid which destroys the follicular cells

40
Q

Why do you discontinue anti-thyroid drugs 7 days before radioactive iodine treatment?

A

to let the thyroid become really active so it will absorb the radioactive iodine

41
Q

What are some of the cautions with this treatment>

A

Avoid contact with children for several weeks

contra-indicated in pregnancy and breast feeding

42
Q

What other molecule can be used instead?

A

Technetium 99 pertechnetate

43
Q

What are the symptoms of viral thyroiditis?

A

dysphagia
pyrexia
hyperthyroidism
raised ESR - eythrocyte sedimentation rate

44
Q

What is viral thyoiditis caused by?

A

Virus attacking the thyroid and causing a fever

45
Q

What are the symptoms caused by?

A

all the thyroxine gets released so presents with hyperthyroidism
meanwhile virus is replicating itself using thyroid

46
Q

What would an iodine thyroid scan show in a patient with viral thyroiditis?

A

not visible on the scan because thyroid gland is not taking up any iodine as not producing any thyroxine

47
Q

What is the treatment of viral thyroiditis?

A

Nothing, wait for virus to go

48
Q

Why will the patient present with hyperthyroidism and then hypothyroidism?

A

all thyroxine released at beginning

when virus gone, no stores left so hypo

Endocrinology (18 decks)

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