Hypothyroidism

Question 1

What are the causes of hypothyroidism?

Answer 1

• Primary (myxoedema) - AI damage to thyroid
• Secondary to pituitary disorder (no TSH)
• Postpartum hypothyroidism (AI)
• Iodine deficiency
• Congenital disease - defective/absent thyroid gland
• Over-treatment for hyperthyroidism
• Thyroid surgery
• Radiotherapy to head + neck
• Drugs, e.g. lithium

Question 2

What are the clinical features of hypothyroidism?

Answer 2

• Macroglossia
• Slow speech
• Deepening of voice
• BMR falls
• Bradycardia
• General weakness
• Depression
• Cold intolerance
• Weight gain w/reduced appetite
• Constipation

Question 3

How is hypothyroidism diagnosed?

Answer 3

Thyroid function test - high TSH, low T3/T4

Question 4

What are the different types of thyroid hormone replacement?

Answer 4

1. Thyroxine (T4) replacement - levothyroxine sodium
2. T3 replacement - liothyronine sodium
3. Combined thyroid hormone replacement (T3+T4)

Question 5

What are the adverse effects of thyroid hormone over-replacement?

Answer 5

• Usually associated with low/suppressed TSH
• Skeletal: increased bone turnover, reduction in bone mineral density, risk of osteoporosis
• CV: tachycardia, risk of dysrrhythmia (esp. AF)
• Metabolic: increased energy expenditure, weight loss
• Increased adrenergic sensitivity: tremor, nervousness
  All symptoms of thyrotoxicosis

Question 6

What are the limitations of thyroid hormone replacement?

Answer 6

• T3 is very potent so it’s difficult to get dose right

- If too high, it switches off TSH –> thyrotoxicosis symptoms

Question 7

How is myxoedema coma treated?

Answer 7

i.v. liothyronine sodium (T3)

Then oral levothyroxine sodium (T4) if possible