Drugs for Thyroid Disease Flashcards
What are some thyroid agents?
- Levothyroxine (T4)
- Liothyronine (T3)
- Liotrix (4:1 ratio of T4:T3)
- Thyroid desiccated
What are some anti-thyroid agents?
- Radioactive iodine
- Potassium iodide
- Methimazole
- Propylthiouracil (PTU)
What is a better thyroid hormone?
- T3
- T4 is a reserved version of T3
What do thiocyanate and perchlorate do in the biosynthesis of thyroid hormones?
- Common environmental pollutants
- Disrupt normal thyroid function and reduce the uptake of iodine
- Competitive inhibition of uptake at the sodium-iodide symporter
What does propranolol do in thyroid storm?
- Inhibits conversion of T4 to T3
- May reverse reduced systemic vascular resistance
What can amiodarone cause?
- Type II amiodarone induced thyrotoxicosis occurs from actual thyroid tissue destruction
What is needed from patients when they start on amiodarone?
- Baseline measures of TSH, free T3, and T4
- Repeat every 6-12 months
What is amiodarone used for?
- Arrhythmias
How does amiodarone cause thyrotoxicosis?
- Each 200mg tablet of amiodarone has 7.4 mg of iodine that is released
- Daily recommendation is 0.15 mg
What is type I amiodarone induced thyrotoxicosis?
- Patients with underlying thyroid pathology such as autonomous nodular goiter or Graves’ disease
What is type II amiodarone induced thyrotoxicosis?
- Result of amiodarone causing a subacute thyroiditis with release of preformed thyroid hormones into circulation
When is methimazole use?
- When thyroid gland produces excess thyroid hormone
- Usually before thyroid surgery
What does methimazole block?
- Iodide organification
What are some side effects with methimazole?
- Agranulocytosis
- Leukopenia
- Thrombocytopenia
- Aplastic anemia
- Liver inflammation
Why is methimazole taken before surgery?
- To lower thyroid hormone levels
- Minimize the effects of thyroid manipulation
- Inhibits the enzyme thyroperoxidase which catalyzes a necessary step in the synthesis of T3/T4
What is potassium iodide?
- Stable form of iodine
- Blocks iodine uptake
What is potassium iodide used for?
- Treatment for hyperthyroidism
- Treatment for iodine deficiency
- And used with anti-thyroid meds to prepare thyroid for surgical removal
What does potassium iodide do in radiation exposure?
- Protects by shrinking the thyroid gland
- Decreases thyroid hormone production
What are the indications of using PTU?
- Patients with Graves’ disease
- Patients with toxic multi-nodular goiter
- Intolerant of methimazole
- Surgery or radioactive iodine therapy is not appropriate
What is PTU used for?
- Ameliorate symptoms of hyperthyroidism
- In preparation of thyroidectomy
- In radioactive iodine therapy in patients who are intolerant of methimazole
What does PTU do?
- Inhibits synthesis of thyroid hormones in hyperthyroidism
- Inhibits the conversion of thyroxine to T3 in peripheral tissues
What doesn’t PTU do?
- Inactivate pre-existing T4/T3
- Interfere with the effectiveness of thyroid hormones given by mouth or by injection
What is levothyroxine used for?
- Treat thyroid hormone deficiency
What is levothyroxine?
- Manufactured T4 which is converted to T3
- Max effect can take up to 6 weeks
