Table 2.
Common features of the two main forms of amiodarone-induced thyrotoxicosis (AIT 1 and AIT 2)
| AIT 1 | AIT 2 | |
|---|---|---|
| Underlying thyroid abnormalities | Yes | Usually noa |
| Colour-flow Doppler sonography | Increased vascularity | Absent hypervascularity |
| Thyroidal RAIU | Low/normal/increasedb | Suppressed |
| Thyroid autoantibodies | Present if AIT is due to Graves disease | Usually absentc |
| Onset time after starting amiodarone | Short (median 3 months) | Long (median 30 months) |
| Spontaneous remission | No | Possible |
| Subsequent hypothyroidism | No | Possible |
| First-line medical treatment | Antithyroid drugsd | Oral glucocorticoids |
| Subsequent definitive thyroid treatment | Generally yes | No |
RAIU, radioiodine uptake.
a
A small goitre may be present.
b
In iodine-replete areas RAIU is always suppressed.
c
Anti-thyroglobulin and anti-thyroid peroxidase antibodies do not allow a diagnosis of AIT 1.
d
Antithyroid drugs (thionamides) may be associated (for a few weeks) with sodium perchlorate.