Thyroid drugs

Question 1

What is the mechanism of carbimazole?

Answer 1

Stops the thyroid peroxidase enzyme from coupling and iodinating tyrosine

Question 2

What are the side effects of carbimazole?

Answer 2

1. Delayed onset
2. Rash
3. GI upset
4. Agranulocytosis
5. Treatment 1-2 years, relapse is 50%

Question 3

What is the mechanism of propythiouracil?

Answer 3

1. Binds to peroxidase and stops iodination of tyrosine

Question 4

What are the side effects of propylthiouracil?

Answer 4

1. Higher rate of agranulocytosis
2. Inhibition of peripheral de-iodination
3. Reserved for those intolerant of carbimazole

Question 5

What is radioactive iodine?

Answer 5

1. Complete destruction of the gland by beta radiation
2. Decays with half-life of 8 days
3. Requires subsequent T4 replacement

Question 6

What can cause hypothyroidism?

Answer 6

1. Atrophic
2. Primary myxoedema
3. Hashimotos
4. Drugs - lithium, amiodarone