Thyroid Hormones Flashcards

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1
Q

Give an example of a thyroid hormone?

A

Levothyroxine

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2
Q

What is the mechanism of action of levothyroxine?

A

Replaces low level of thyroxine in patients with underachieve thyroid glands, which in turn suppresses high TSH by negative feedback

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3
Q

What are the symptoms of hypothyroidism?

A
  • Lethargy
  • Tiredness
  • Weight gain
  • Thinning of skin and hair
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4
Q

What is an over-replacement of thyroxine characterised by?

A

Normal thyroxine level with a low TSH level

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5
Q

What is the route of delivery of levothyroxine?

A

PO

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6
Q

What are the indications for thyroxine?

A
  • Primary hypothyroidism
  • As ‘replace’ element of ‘block and replace’ regimen for hyperthyroidism
  • Goitre
  • Hashimoto’s thyroiditis
  • Thyroid carcinoma
  • Hypopituitarism
  • Pregnancy-related hypothyroidism
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7
Q

What are the contraindications to thyroxine?

A

Thyrotoxicosis

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8
Q

When should thyroxine be used with caution?

A
  • Long-standing hypothyroidism
  • Adrenal insufficiency
  • Angina and cardiovascular disorders
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9
Q

What monitoring is required with thyroxine?

A
  • Baseline ECG when starting drug

- TFTs

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10
Q

Why should a baseline ECG be done when starting thyroxine?

A

For comparison with future ECGs taken if patients develop cardiovascular side-effects from the thyroid hormone replacement

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11
Q

When should TFTs be done with thyroxine?

A

3 months after starting treatment or changing dose, and annual once stable

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12
Q

When should maternal thyroid function be assessed?

A
  • Before conception
  • Diagnosis of pregnancy
  • During 2nd and 3rd trimester
  • After delivery
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13
Q

What might need to happen to levothyroxine dose during pregnancy?

A

May need to be increased

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14
Q

What needs to be done if thyroxine dose is changed during pregnancy?

A

Increased monitoring of thyroid function

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15
Q

What should be considered with long-term treatment with thyroxine?

A

Consider supplementation with vitamin D

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16
Q

What might thyroxine interact with?

A
  • Warfarin
  • Antacids
  • Calcium
  • Iron salts
  • CYP450 inducers
17
Q

What might happen if warfarin is given with thyroxine?

A

Enhanced anticoagulant effect

18
Q

How should you avoid concurrent use of thyroxine and antacids, calcium, and iron salts?

A

Maintaining 4 hour gap

19
Q

What pneumonic can be used to remember CYP450 inducers?

A

PC BRAS

Phenytoin
Carbamazepine
Barbiturates 
Rifampicin
Alcohol
Sulphonylureas
20
Q

What are the common side effects of thyroxine?

A
  • GI upset
  • Palpitations
  • Tremor
  • Angina
  • Goitre
  • Restlessness
  • Flushing
  • Headache
21
Q

What are the less common side effects of thyroxine?

A
  • Angina
  • Muscular weakness
  • Weight changes
  • Insomnia
  • Mood changes
22
Q

What patient counselling is required with thyroxine?

A
  • Mode of action
  • How to take
  • Duration of treatment and monitoring
  • Dosing
  • Compliance
  • Signs of thyrotoxicosis
23
Q

What should the patient be told about the mode of action of thyroxine?

A

Explain this medication contains a hormone that the patients body is not producing to an adequate level and as a result the patient is experiencing symptoms

24
Q

What should the patient be told regarding how to take thyroxine?

A

Preferred to take levothyroxine in the morning 30 minutes to 1 hour before having breakfast or taking other medications

25
Q

What should the patient told regarding duration of treatment with thyroxine?

A

Inform the patient that treatment is likely to be lifelong and that regular blood tests will be required to monitor thyroid function

26
Q

What should the patient be told regarding dosing of thyroxine?

A

Thyroid hormone replacement is normally taken once daily. The patient will be started on the minimum dose, and the dose will be titrated up if required

27
Q

What should the patient be told regarding compliance with thyroxine?

A

It is important the patient takes the drug as directed and that the patient does not stop taking the drug on their own initiative

28
Q

What are the signs of thyrotoxicosis?

A
  • Palpitations
  • Arrhythmias
  • Angina
  • Tremor
  • Diarrhoea