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LCRS 1 > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

1
Q

State two common causes of hyperthyroidism.

A

Graves’ Disease

Plummer’s Disease (toxic nodular goitre)

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2
Q

What type of disease is Graves’? Describe its mechanism.

A

Autoimmune
An autoimmune antibody is produced that behaves like TSH and binds to the TSH receptor thus stimulating thyroid hormone production

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3
Q

What does a thyroid gland look like in Graves’ Disease?

A

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

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4
Q

State some features of Graves’ Disease.

A 
Rapid pulse 
Warm 
Localised pretibial myxoedema 
Exophthalmos 
Excitability/nervousness 
Loss of weight  
Muscle wasting  
Oligomenorrhoea/amenorrhoea
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5
Q

What are two defining features of Graves’ and what is it caused by?

A

Localised pretibial myxoedema
Exophthalmos
Antibodies cause both of these

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6
Q

Describe the appearance of a thyroid gland of a Graves’ patient in a thyroid scan using radioactive iodine.

A

The whole gland is smoothly enlarged and the whole gland is overactive

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7
Q

What causes Plummer’s Disease?

A

It is caused by a benign adenoma in the thyroid gland

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8
Q

How does Plummer’s disease differ from Graves’?

A

NO pretibial myxoedema
NO exophthalmos
NOT autoimmune

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9
Q

What will a technetium or iodine scan of the thyroid show in a patient with Plummer’s Disease?

A

All the iodine will be taken up by the overactive, tumorous part of the thyroid so you will see a hot nodule appear
The rest of the thyroid gland will not be seen because the high thyroxine production will decrease TSH release from the anterior pituitary and so the rest of the thyroid gland that is responding to TSH will not produce any thyroxine and will not take up iodine

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10
Q

Describe the effects of thyroxine on the sympathetic nervous system.

A

Thyroxine sensitises beta adrenoceptors to ambient levels of adrenaline and noradrenaline
So you get symptoms of having high adrenaline

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11
Q

What is thyroid storm (thyrotoxic crisis) and what are the features of thyroid storm?

A 
This is a medical emergency that is a rare but important complication of hyperthyroidism  
Features: 
Hyperpyrexia 
Accelerated tachycardia/arrhythmia 
Cardiac failure  
Delirium/frank psychosis  
Hepatocellular dysfunction, jaundice
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12
Q

State four drug treatments for hyperthyroidism.

A

Thionamides
Potassium Iodide
Radioiodine
Beta Blockers

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13
Q

State two thionamides.

A

Propylthiouracil

Carbimazole

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14
Q

What are thionamides used to treat and when would you use it?

A

Graves’ Disease
Plummer’s Disease
You can use it before thyroidectomy to stabilise the patient (you wouldn’t want to give general anaesthetic to someone who is tachycardic with a labile heart rate)
It can be used after radioiodine treatment while you’re waiting for the clinical effects of the treatment

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15
Q

Describe the synthesis of thyroxine by follicular cells.

A

Thyroglobulin is a protein produced by the follicular cells
Iodine is taken up by the follicular cells
Thyroid peroxidase, in the presence of hydrogen peroxide, iodinates the tyrosyl residues on the thyroglobulin to produce monoiodotyrosine or diiodotyrosine
Peroxidase transaminase then couples MIT and DIT to form T3 and T4, which is stored in the colloid

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16
Q

What is the mechanism of action of thionamides?

A

Thionamides inhibit thyroperoxidase
This prevents the iodination of thyroglobulin and coupling of MIT and DIT
It also inhibits peroxidase transaminase

17
Q

Why do thionamides have a delayed effect on thyroid hormone levels?

A

Thionamides are quick in inhibiting synthesis of thyroid hormone but it does nothing to the thyroid hormone that has already been synthesised and is stored in the colloid ready for release
So there is a big delay between the biochemical effects and the clinical effects

18
Q

What would you give the patient temporarily whilst waiting for thethionamides to have their clinical effect?

A

Non-selective beta-blockers

This will reduce the effects of beta sensitisation by thyroxine

19
Q

Other than its main function in inhibiting thyroperoxidase, what else do thionamides do?

A

Suppress antibody production (in Graves’)

Reduces deiodination of T4 to T3

20
Q

State some unwanted effects of thionamides.

A 
Agranulocytosis/granulocytopenia 
Nausea 
Headaches  
Rashes 
Jaundice 
Joint pain
21
Q

Carbimazole is a pro-drug. What is it converted to become active?

A

Methimazole

22
Q

What are the implications of thionamides in pregnancy?

A

Thionamides can cross the placenta and is present in breast milk so it can cause foetal hypothyroidism
This means that you would want to give as low a dose as possible to a patient who is trying to conceive and is taking thionamides
Both drugs cross into breast milk but PTU does this less than CBZ
It is metabolised in the liver and excreted in the urine

23
Q

What is the mechanism of action of potassium iodide treatment?

A

If you give a massive dose of iodine it can turn off the thyroid gland
It inhibits the iodination of thyroglobulin and inhibits the production of hydrogen peroxide

24
Q

What is the Wolff-Chaikoff effect?

A

The temporary reduction in thyroid hormones following ingestion of a large amount of iodine

25
Q

Why is potassium iodide useful before surgery?

A

It reduces the size and vascularity of the thyroid gland

26
Q

State some unwanted actions of potassium iodide.

A

Rashes
Fever
Angioedema

27
Q

In what form is potassium iodide given?

A

Lugol’s Solution or Aqueous iodine

28
Q

What is radioiodine use to treat?

A

Iodine 131 is used to treat Graves’ Disease, Plummer’s Disease and Thyroid Cancer

29
Q

Describe the mechanism of action of radioiodine.

A

Radioiodine is taken up by the thyroid gland and it accumulates in the colloid
From the colloid it emits beta particles that destroy the follicular cells

30
Q

Describe the pharmacokinetics of radioiodine.

A

It is given orally as a single dose
Discontinue anti-thyroid drugs 7-10 days before radioiodine treatment to allow time for the thyroid to become really active again so that it takes up a lot of thyroid hormone
Radioactivity is negligible after 2 months

31
Q

What are some cautions of radioiodine?

A

Avoid close contact with small children for several weeks after receiving radioiodine
Contra-indicated in pregnancy and breast feeding

32
Q

Name another molecule that is cheaper and can be used instead of radioiodine.

A

Technetium 99 Pertechnetate

33
Q

4 types of throid cancer and order of malignancy and incidence

A

Papillary
Follicular
Medullary
Anaplastic

Down decreases incidence and malignancy

34
Q

Way to remember throid cancer types

A

Please forget my aconym

35
Q

What is De Quervains thyroiditis

A

Viral inflammation of thyroid

36
Q

Sign of de quervains thyroiditis

A

Constitutional symptoms: fever, joint pain and fatigue
Transient hyperthyroid symptoms with a painful throat
Transient hypothyroid symptoms
Resolving illness with euthyroid status

37
Q

Treatment of thyroid cancer

A

Radioiodine

LCRS 1 (58 decks)

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