Antithyroid Drugs
Start with the big picture
Thioamides such as methimazole and propylthiouracil inhibit thyroid peroxidase steps involved in hormone synthesis; PTU also reduces peripheral conversion of T4 to T3. Their clinical effect is delayed while stored hormone is depleted. Methimazole is preferred for most patients, while PTU has specific roles, including first-trimester pregnancy and thyroid storm, but carries a risk of severe hepatotoxicity. Other approaches include iodide to acutely inhibit hormone release, radioactive iodine to ablate the gland, and less commonly used ionic inhibitors. Iodinated contrast agents, β-blockers, and glucocorticoids can provide adjunctive effects. The lesson also highlights contraindications, adverse effects, and the need to recognize possible agranulocytosis promptly.
What you'll learn
- Explain how thioamides inhibit thyroid hormone synthesis and how PTU has an additional effect.
- Describe the delayed onset of thioamide clinical effects and key considerations in selecting an agent.
- Compare the roles, mechanisms, and important contraindications of iodide and radioactive iodine.
- Identify major adverse effects of antithyroid drugs and the response to suspected agranulocytosis.
- Summarize the adjunctive roles of ionic inhibitors, iodinated contrast agents, β-blockers, and glucocorticoids.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
