Thyroid drugs: thionamides, levothyroxine and radioactive iodine
Where each thyroid drug acts on hormone synthesis, release and peripheral conversion, why thionamides take weeks to work, how carbimazole and propylthiouracil differ in pregnancy and toxicity, the iodine effects (Wolff-Chaikoff, Jod-Basedow, amiodarone), levothyroxine kinetics and interactions, and how radioactive iodine works.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Thyroid hormone is made in steps: iodide uptake, oxidation and organification, coupling, storage in thyroglobulin, release, and peripheral conversion of T4 to T3. Each drug acts at a defined step.
- Thionamides block synthesis, not release, so they take weeks.
- Iodine in large amounts blocks release acutely but can also fuel excess synthesis in autonomous glands.
Loading the rest of the note…
Finished reading?
Sources
- Endocrinology (Therapeutic Guidelines)AU/NZTherapeutic Guidelines Ltd, 2026
- Australian Medicines HandbookAU/NZAustralian Medicines Handbook Pty Ltd, 2026
- 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosisRoss et al., Thyroid 2016;26:1343-1421, 2016
- 2018 European Thyroid Association guideline for the management of Graves' hyperthyroidismKahaly et al., Eur Thyroid J 2018;7:167-86, 2018
- 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartumAlexander et al., Thyroid 2017;27:315-89, 2017
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Turnstile bot check on sign-in and signed-out feedback