Iodine-Induced Hyperthyroidism
Iodine-induced hyperthyroidism (IIH) is a form of hyperthyroidism caused by excess dietary or supplemental iodine. Unlike graves-disease, it is not autoimmune in origin.
Causes
Two distinct mechanisms:
- Excess iodine intake — from high-dose iodine supplements, kelp, iodized salt, seafood, iodine contrast dyes used in medical imaging, or iodine-containing medications (e.g., cough syrups, amiodarone).
- Correction of iodine deficiency — in iodine-deficient regions, repleting iodine can initially trigger transient hyperthyroidism in individuals whose thyroid glands had become autonomously functioning.
Features
- Uncommon in the U.S. (where iodine sufficiency is the norm) but possible
- Usually temporary
- May still require medical intervention, especially if thyroid nodules develop
Management
- Identify and remove the iodine source (supplement, food, medication, contrast agent)
- Follow a low-iodine-diet if dietary excess is the cause
- Medical treatment may be needed if the condition does not resolve