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
What is secondary hyperthyroidism caused by?
TSH secreting pituitary tumour
What are the symptoms of hyperthyroidism?
- Breathlessness
- Heat intolerance
- Diarrhoea
- Infertility
- Polyuria
What can be added to provide adrenergic symptom relief in hyperthyroidism?
- Propranolol (10-40mg 3-4x)
- Diltiazem - alt for asthma
Radio iodine
- Damage to DNA, thyroid cell death
- Close + prolonged contact w/ children + pregnant women = avoided for 3 weeks after
- Avoid being pregnant for 6 months (women) + 4 months (men)
What are the adverse effects of carbimazole?
- Nausea
- Headache
- Itch + rash: treated w. antihistamines
- Bone marrow suppression: occurs STOP
- Jaundice
- Neutropenia + agranulocytosis
What is the dose for carbimazole?
- 15-40mg daily
- Maintenance: 5-15 mg
- Block + replace = 40-60mg daily
What are the adverse effects of propylthiouracil?
- Leucopenia (reversible)
- Agranulocytosis
- Hepatitis
What is the dose for propylthiouracil?
- 200-400mg daily
- Maintenance dose: 50-150mg
