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BRS Flashcards (Y2) > Hyperthyroidism > Flashcards

Hyperthyroidism Flashcards

1
Q

What level of TSH will you find in a patient with primary hypothyroidism, where the thyroid gland has been destroyed by the immune system?

A

High TSH

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2
Q

How do you control thyroid replacement in primary hypothyroidism?

A

By monitoring TSH levels (until dose falls to normal)

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3
Q

Describe Graves’ Disease and its pathophysiology

A

Autoimmune
Antibodies bind to and stimulate the TSH receptor in the thyroid
Causes goitre (smooth) and hyperthyroidism

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4
Q

List symptoms of Graves’ Disease

A

Weight loss despite increased appetite
Tachycardia, palpitations
A/oligomenorrhoea
Heat intolerance
Sweating
Tremor
Exophthalmos
Muscle wasting
Localised myxoedema (not to be confused with hypothyroidism)

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5
Q

What causes exophthalmos?

A

Other antibodies bind to muscles behind the eye, causing them to grow - pushes eyes forward

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6
Q

What is pretibial myxoedema?

A

The swelling (non-pitting) that occurs on the shins of patients with Graves’ disease - growth of soft tissue (hypertrophy caused by antibodies)

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7
Q

What changes to the thyroid gland are observed in Graves’ Disease and how does this present on a thyroid scan?

A

Diffuse enlargement and engorgement of thyroid gland
Thyroid scan: Diffuse goitre of moderate size and uniform radioiodine uptake

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8
Q

What are the characteristics of Plummer’s Disease (toxic nodular goitre)?

A

Benign overactive adenoma that produces thyroxine
Not autoimmune
No pretibial myxoedema
No exophthalmos

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9
Q

Why is there atrophy of the normal functioning thyroid gland when there is a toxic nodular goitre?

A

The thyroxine being released from the tumour suppresses TSH so the normal gland doesn’t work as much.

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10
Q

How would a toxic nodular goitre present on a thyroid scan?

A

‘Hot nodule’ - single nodule of radio-iodine uptake

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11
Q

What effect does thyroxine have on the sympathetic nervous system and what is the relevance of this?

A

Sensitises beta adrenoceptors to ambient levels (slight changes) of adrenaline and noradrenaline
Thus there is apparent sympathetic activation
Causes tachycardia, palpitations, tremor in hands, lid lag
Patient with hyperthyroidism - slight scare, HR will rocket

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12
Q

What are some symptoms of hyperthyroidism?

A

Weight loss despite increased appetite
Breathlessness,
palpitations, tachycardia
Sweating
Heat intolerance
Diarrhoea
Lid lag and other sympathetic features

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13
Q

What are the symptoms of a thyroid storm?

A

Hyperpyrexia > 41oC
Accelerated tachycardia / arrhythmia
Cardiac failure
Delirium / frank psychosis
Hepatocellular dysfunction; jaundice

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14
Q

How is thyroid storm identified?

A

Two symptoms + hyperthyroidism (confirmed by blood test)

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15
Q

How is thyroid storm diagnosed?

A

Two symptoms + hyperthyroidism (confirmed with blood tests)

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16
Q

What are the treatment options for hyperthyroidism?

A

Thyroidectomy
Radioiodine
Drugs

17
Q

What drugs are used to treat hyperthyroidism?

A

Thionamides (anti-thyroid drugs) e.g. carbimazole, propylthiouracil (PTU)
Potassium iodide (KI)
Radioiodine
Beta-blockers

18
Q

What is the mechanism of action of thionamides?

A

Inhibition of thyroid peroxidase and hence inhibition of T3/4 synthesis and
secretion

19
Q

How long does it take to see the clinical effect of thionamides and what medication should be taken with them as a result?

A

Weeks - follicular cells have a month store of thyroxine
Beta blockers, e.g. propranolol are taken to rapidly reduce symptoms - tremors, palpitations

20
Q

What are the unwanted side effects of thionamides?

A

Agranulocytosis (usually reduction in neutrophils) - rare and reversible on withdrawal of drug - e.g. sore throat - strep in throat starts to multiply
Rashes (relatively common)

21
Q

What is the follow-up for thionamides?

A

Aim to stop ATD treatments within 18 months
Review patient periodically including thyroid function tests for remission/relapse

22
Q

What is the role of beta blockers in thyrotoxicosis?

A

Takes several weeks for ATDs to have clinical effects (reduced tremor, slower heart rate, less anxiety) so NON-selective (ie b1 & b2) beta blocker, e.g. propranolol achieves these effects in the interim

23
Q

What is the dose of KI and what is it used for?

A

Dose 30x the average daily requirement
Used to prepare hyperthyroid patients for surgery and in severe thyrotoxic crisis (thyroid storm)

24
Q

What is the mechanism of potassium iodide?

A

Inhibition of thyroid hormone synthesis & secretion:
- Inhibits iodination of thyroglobulin
- Inhibits H2O2 generation (+ thyroperoxidase)
WOLFF–CHAIKOFF effect - presumed autoregulatory effect

25
Q

Why can’t KI be used for more than 10 days?

A

After 10 days, the iodine is used to make more thyroxine

26
Q

What is the effect of potassium iodide?

A

Hyperthyroid symptoms reduce within 1-2 days
Vascularity and size of gland reduce within 10-14 days

27
Q

What are the risks of thyroid surgery?

A

Risk of voice change
Risk of also losing parathyroid glands
Scar
Anaesthetic

28
Q

How is Radioiodine administered?

A

Swallow a capsule containing about 370 MBq (10 mCi) of the isotope I (131)

29
Q

What precautions must be taken when taking Radioiodine?

A

Contraindicated in pregnancy
Need to avoid children and pregnant mums for a few days

30
Q

What can used instead of Radioiodine if you only require a scan and not treatment?

A

99-Tc pertechnetate

31
Q

List characteristics of Viral (de Quervain’s) thyroiditis

A

Painful dysphagia
Hyperthyroidism
Pyrexia (fever)
Thyroid inflammation

32
Q

Why is there no iodine uptake in viral thyroiditis?

A

Virus attacks thyroid gland causing pain and tenderness
Thyroid stops making thyroxine and makes viruses instead

33
Q

Describe a thyroid scan for viral thyroiditis?

A

No iodine uptake - blank

34
Q

Outline the progression of viral thyroiditis

A

Virus attacks thyroid gland causing pain and tenderness
Thyroid stops making thyroxine and makes viruses instead
Thus no iodine uptake (ZERO)
Stored thyroxine released - FT4 levels rise, TSH falls - hyperthyroid
Four weeks later, stored thyroxine exhausted, so hypothyroid
After a further month, resolution occurs (like in all viral diseases)
Slow recovery after 3 months - becomes euthyroid again

35
Q

What’s the difference between viral thyroiditis and postpartum thyroiditis?

A

Postpartum thyroiditis - similar but no pain and only occurs after pregnancy - immune system modulated during pregnancy

BRS Flashcards (Y2) (79 decks)

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