Table.
Comparison between amiodarone-induced thyrotoxicosis type 1 and type 2∗
| Type 1 (Graves-like) | Type 2 (Thyroiditis-like) | |
| Preexisting or latent thyroid disease | Usually present | Absent |
| Prevalence | More common in iodine-deficient areas | More common in iodine-replete areas |
| Duration of amiodarone intake | Usually shorter (<1–2 yrs) | Usually longer (>2 yrs) |
| Pathogenesis | Unregulated hormone synthesis due to excess iodine load (Jod Basedow phenomenon) | Inflammatory destruction of the gland related to direct cytotoxic effect of amiodarone |
| Thyroid examination | Goiter more likely to be present | Normal or tender thyroid gland |
| Thyroid autoantibodies | More likely to be present | Likely absent |
| Radioactive iodine uptake scan (24-hr values) | Increased uptake (>30%) | <1% |
| Interleukin-6 | Normal | High |
| Color-flow Doppler sonography | Increased parenchymal blood flow | Normal or decreased blood flow |
| Treatment | Stop amiodarone; thionamides; perchlorate or lithium | Amiodarone discontinuation may not be required; glucocorticoids |
| Subsequent hypothyroidism | Uncommon | Common |