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LCRS Endocrinology > 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 enlarged (goitre) 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)

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4
Q

How does a patient with Graves’ normally present?

A 
Overactive
Anxious
Rapid pulse
Warm
Localised pretibial myxoedema 
Exopthalamos
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5
Q

What is localised pretibial myxoedema?

A

Swelling of soft tissue in shins due to antibody binding to receptor

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6
Q

What is exopthalmos?

A

Another antibody binds to growth factor receptors behind the eye so muscles behind the eye grow and push the eye forward

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7
Q

What makes exopthalmos worse?

A

Smoking

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8
Q

What is the thyroid gland of someone with Graves’ like?

A

Very diffuse and smoothly enlarged

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9
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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10
Q

What is Plummers disease?

A

Toxic nodular goitre- part of the thyroid has become tumorous and is misbehaving

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11
Q

What is Plummer’s disease caused by?

A

A benign adenoma that is overactive at making thyroxine

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12
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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13
Q

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

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

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14
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

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15
Q

What does the effect of thyroxine on sympathetic nervous system cause in patients?

A 
Effects of too much adrenaline:
Palpitations
Heart tremors
Tachycardia
Lidlag
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16
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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17
Q

What is a thyrotoxic crisis known as?

A

Thyroid storm

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18
Q

What is the mortality of a thyroid storm if untreated?

A

50%

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19
Q

What are the features of a thyroid storm?

A 
Hyperpyrexia
Accelerated tachycardia/arrhythmia
Cardiac failure
Delirium
Hepatocellular dysfunction/jaundice
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20
Q

What is hyperpyrexia?

A

Temperature > 41 degrees

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21
Q

What is the treatment for a thyroid storm?

A

Surgery
Radioiodine
Drugs

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22
Q

What sort of drugs are used to treat hyperthyroidism?

A

Thionamides- Propylthiouracil and Carbimazole
Potassium iodide
Radioiodine
Beta blockers

23
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

24
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

25
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

26
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

27
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

28
Q

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

A

Non-selective beta blocker

29
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)

30
Q

What are the unwanted effects of thionamides?

A 
Agranulocytosis/granulocytopenia
Rashes
Headaches
Nausea
Jaundice 
Joint pain
31
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

32
Q

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

A

PTU crosses into the breast milk less than carbimazole

33
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

34
Q

When is iodine used as treatment for hyperthyroidism?

A

Preparation of patients for surgery

Severe thyroid storm

35
Q

How does iodine treatment work?

A

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

36
Q

What is the Wolff-Chaikoff effect?

A

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

37
Q

Why does the Wolf-Chaikoff effect occur?

A

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

38
Q

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

A

Iodine is quicker

39
Q

What are the unwanted actions of iodine treatment?

A

Allergic reaction
Rashes
Fever
Angioedema

40
Q

How is iodine administered?

A

Lugol’s solution or aqueous

41
Q

What is radioiodine used to treat?

A

Graves’, Plummer’s and thyroid cancer

42
Q

What does radioiodine treatment do?

A

Permanently switches off the thyroid without needing surgery

43
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

44
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

45
Q

What is technetium 99 pertechnetate used for?

A

Thyroid uptake scans

46
Q

How does the thyroid uptake scan for Graves look like?

A

Whole thyroid is active and smoothly enlarged

47
Q

How does the thyroid uptake scan for Plummers/Toxic nodule look like?

A

Single focus of activity and rest is suppressed

48
Q

How does the thyroid uptake scan for thyroiditis look like?

A

Whole thyroid is unhappy, enlarged and inactive

49
Q

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

A

Iodine

50
Q

What are the symptoms of viral thyroiditis?

A 
Dysphagia
Pyrexia
Malaise
Pain radiating to the ear
Thyroid gland visibly enlarged and tender (on one side)
51
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

52
Q

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

A

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

53
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

LCRS Endocrinology (18 decks)

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