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RR ENDO > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

1
Q

What are two common causes of hyperthyroidism?

A 
Graves' disease
Nodular goitre (Plummer's disease)
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2
Q

What is Graves’ disease?

A

Autoimmune disease- antibodies bind to and stimulate TSH receptor in thyroid. This makes the thyroid overreactive and this leads to the thyroid becoming smoothly (goitre) enlarged and you get hyperthyroidism

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3
Q

In terms of the eyelids, how can you tell if a person has hyperthyroidism?

A

It causes lid lag (delay in eyelid moving down as you look down)

  • nerve of eye under sympathetic ocntrol
  • T4 makes B receptor more sensitive to adrenaline- Increase heartrate also as aresult
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4
Q

What is localised pretibial myxoedema?

A

hypertrophy of soft tissue in shins due to antibody binding to receptor– non pitting oedema

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5
Q

What is exopthalmos?

A

Another antibody binds to growth factors on muscles behind the eye –grow and push the eye forward

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6
Q

Pretibial myxoedema and exopthlamos is specific to

A

Grave’s

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7
Q

How can you image the thyroid?

A

By giving a patient radioactive iodine which will show up on a scintigram

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8
Q

What is Plummers disease?

A

Toxic nodular goitre- part of the thyroid has benign adenoma and is misbehaving

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9
Q

What is Plummer’s disease caused by?

A

A benign adenoma that is overactive at making thyroxine

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10
Q

What is the thyroid gland of someone with Plummer’s like?

A

There will be a visible lump on one side

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11
Q

What will you see if you do an iodine scan on someone with Plummer’s?

Antibody test

A

It will show the iodine going into the hot tumour. Because there is so much thyroxine coming from the tumour, the pituitary will stop making TSH and the rest of the thyroid will shrink away and stop making thyroxine so only the nodule is visible

Antibody test is negative as it is not due to autoimmune

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12
Q

What is the effect of thyroxine on the sympathetic nervous system?

A

It sensitises beta adrenoceptors to adrenaline and noradrenaline so normal amounts will have much stronger effects

Tachycardia, palpitations, tremor, lid lag

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13
Q

Give a brief summary of the symptoms of hyperthyroidism

A 
Weight loss despite increased appetite 
Breathlessness
Tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag
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14
Q

What is a thyrotoxic crisis known as?

A

Thyroid storm– medical emergency

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15
Q

What is the mortality of a thyroid storm if untreated?

A

50%

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16
Q

What are the features of a thyroid storm?

A 
Hyperpyrexia
Accelerated tachycardia/arrhythmia
Cardiac failure
Delirium
Hepatocellular dysfunction/jaundice
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17
Q

What is hyperpyrexia?

A

Temperature > 41 degrees

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18
Q

What is the treatment for a thyroid storm?

A

Surgery
Radioiodine
Drugs

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19
Q

What sort of drugs are used to treat hyperthyroidism?

A 
Thionamides- Propylthiouracil and Carbimazole
Potassium iodide
Radioiodine
-These reduce thyroid hormone synth
Beta blockers-- propanalol non selective
-Relieve symptoms
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20
Q

When are thionamides specifically given?

A
  • Before thyroidectomy because you don’t want to give a general anaesthetic to someone who is tachycardic
  • Following radioactive iodine treatment
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21
Q

How are thyroid hormones synthesised?

A

Iodine is taken up into follicular cells
Under the action of thyroperoxidase with hydrogen peroxide you get iodination of tyrosine residues in the thyroglobulin
You then get coupling of monoiodotyrosine and diiodotyrosine to form T3 and T4
This is taken up and released by cells into the circulation

22
Q

What do thionamides do?

A

They inhibit thyroperoxidase hence inhibit iodination of tyrosine residues and coupling of tyrosine residues
So leads to reduction in production and secretion of T3 and T4

23
Q

How long does it take for both the biochemical and clinical effects of thionamides take to become evident?

A

Biochemical- Hours

Clinical- A few weeks

24
Q

Why is there this relationship between biochemical and clinical presentation?

A

There is a lot of stored thyroid hormone in follicular cells and the anti thyroid treatment only affects synthesis not storage

25
Q

Due to the delayed clinical effect of thionamides, how would you deal with the symptoms in the short term?

A

Propanalol: Non-selective beta blocker

26
Q

What are some other effects of anti thyroid hormones?

A

Suppress antibody production in Graves disease

Reduces the deiodination of T4 to T3 in peripheral tissues (done by propylthiouracil)

27
Q

What are the unwanted effects of thionamides?

Administered

Metabolised by and excreted

Follow up consists of

A

Agranulocytosis/granulocytopenia
Rashes

Administered orally

Metabolised by liver and excreted in urine

  • Usually aiming to stop anti-thyroid drug treatment after 18 months– wean off
  • Review patients periodically inc thyroid function tests in case of relapse
28
Q

Why are there concerns relating to pregnancy with thyroid disorder?

A

It is common in women around reproductive age and thionamides are able to cross the placenta and are secreted in the milk which can lead to foetal hypothyroidism

29
Q

Why would a breastfeeding woman be put on PTU over carbimazole?

A

PTU crosses into the breast milk less than carbimazole

30
Q

Why is the beta blocker that you use to treat the symptoms non-selective?

A

Reduces all the effects of excess stimulation of beta adrenoceptors

31
Q

When is iodine used as treatment for hyperthyroidism?

A

Preparation of patients for surgery

Severe thyroid storm

32
Q

How does iodine treatment work?

Hyperthyroid symptoms reduce within how many days

Vascularity and size of gland reduces wihtin how many days

A

You give such a large dose that the thyroid switches off because inhibits iodination of thyroglobulin and generation of hydrogen peroxide

2 days

10-14 days

33
Q

What is the Wolff-Chaikoff effect?

A

There is temporary reduction in thyroid hormones following ingestion of large amounts of iodine

34
Q

Why does the Wolf-Chaikoff effect occur?

A

It is autoregulatory, it occurs to prevent the thyroid form making too much thyroid hormone

35
Q

How does iodine compare to thionamides in terms of time required for effects to be seen?

A

Iodine is quicker

36
Q

What are the unwanted actions of iodine treatment?

A

Allergic reaction
Rashes
Fever
Angioedema

37
Q

How is iodine administered?

A

Orally-Lugol’s solution or aqueous iodine

Max effects after 10 days continuous administration

38
Q

What is radioiodine used to treat?

A

Graves’, Plummer’s and thyroid cancer

39
Q

What does radioiodine treatment do?

A

Permanently switches off the thyroid without needing surgery

40
Q

How does radioiodine work?

A

Thyroid follicular cells take up the iodine and it accumulates in the colloid, from there, it emits beta particles of radiation that destroy the follicular cells

41
Q

7-10 days before radioiodine treatment, anti thyroid drugs are stopped, why is this?

A

This is so that the thyroid gland can become incredibly active so that it will take up a lot of the iodine when it is administered and maximum damage can be achieved

42
Q

How is it administered

A

Single oral dose

43
Q

Radioactive half life of

A

8 days

44
Q

Radioactivity negligible after

A

2 months

45
Q

Radioiodine cautions

A

Avoid close contact with small children for several weeks after
Contraindicated in pregnancy and breast feeding

46
Q

Which drug reduces the size and vascularity of the thyroid gland?

A

Iodide

47
Q

How does the thyroid uptake scan for thyroiditis look like? we didnt cover thyroiditis

What are the symptoms of viral thyroiditis?

A

Whole thyroid is unhappy, enlarged and inactive

Dysphagia
Pyrexia
Malaise
Pain radiating to the ear
Thyroid gland visibly enlarged and tender (on one side)
48
Q

How does viral thyroiditis occur?

A

A virus attacks the thyroid and causes fever, it also damages the thyroid follicles and stored thyroxine is released. So gland is being damaged and prevented from making any new thyroxine but prevents as an overactive thyroid

49
Q

What do you see in a technetium scan for viral thyroiditis?

A

There is no iodine uptake so you don’t see anything

50
Q

How do you treat viral thyroiditis?

A

The patient just has to wait for about month until all the stored thyroxine has ran out and will be hypothyroid until their cells recover

RR ENDO (13 decks)

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