Wk 12: Thyroid in practice Flashcards
How does amiodarone cause hypothyroidism?
Blocks conversion of T4 to T3
How does amiodarone cause hyperthyroidism?
- Due to iodine content of drug
- May mask clinical fts of hyperthyroidism
- May remit spontaneously w/in 6 months
What is the action to take if hypothyroidism occurs when taking amiodarone?
Add levothyroxine + continue amiodarone
How does lithium cause hypothyroidism?
- Inhibits iodine uptake + thyroid hormone release
- Treat w/ conventional levothyroxine replacement
Interpreting TFTs: Inc TSH, Dec T4
Hypothyroidism
Interpreting TFTs: Dec TSH, Inc T4
Hyperthyroidism
Interpreting TFTs: Inc TSH, normal T4
Subclinical hypothyroidism
Interpreting TFTs: Dec TSH, normal T4
Subclinical hyperthyroidism
What is Primary hypothyroidism (95%) + what is the cause of it?
Failure of thyroid gland to produce thyroid hormones
What is secondary hypothyroidism (5%) + what is the cause of it?
Underproduction of TSH by pituitary gland
What are the symptoms of hypothyroidism?
- Cold intolerance
- Weight gain
- Myalgia
- Menstrual irregularities
- Goitre
- Bradycardia
Levothyroxine dose
- 1.6 mcg/kg/day for adults <65
- Inc 25-50mcg every 3-4 weeks
- Maintenance: 100-200mcg
What are the adverse effects of levothyroxine?
- Arrhythmias + tachycardia
- Flushing/fever
- Weight loss
- Hypersensitivity reaction: rash
When should levothyroxine ideally be taken?
30 mins before breakfast, caffeine containing liquid or other drugs
What is primary hyperthyroidism + what is it caused by?
Most commonly Grave’s disease:
- Antibodies stimulate + inc secretion of thyroid hormones
