Features which may help to distinguish between type I and type II amiodarone induced hyperthyroidism
| Type I | Type II | |
| Pre-existing thyroid disease | Yes | No |
| Goitre | Diffuse or nodular | Uncommon, may be tender |
| Radioiodine uptake by thyroid | Low normal | Negligible |
| TSH receptor antibodies in serum | May be present | Absent |
| Antiperoxidase (microsomal antibodies in serum) | May be present | May be present |
| Serum IL-6 | Normal or slightly elevated | Very elevated |
| Subsequent hypothyroidism | No | Possible |
IL-6, interleukin 6.