Q: What are the
2 types of Amiodarone Induced Thyrotoxicosis (AIT)?
Answer:
Type 1 - Which usually affects patients
with latent or previously known thyroid disorders and is more common in areas of
low iodine intake. It is caused by iodine-induced excess thyroid hormone
synthesis and release.
Type 2 - occurs in patients with a
previously normal thyroid gland and is caused by a destructive thyroiditis that
leads to the release of preformed thyroid hormones from the damaged thyroid
follicular cells.
Clinical Significance: Type 2 thyrotoxicosis may respond to course of glucocorticoids,
which has membrane-stabilizing and anti-inflammatory effects, as well
as glucocorticoids reduce conversion of T4 to T3. Dose is prednisone to start with 30-40 mg/d and taper over a
couple of months until free T4 levels are within the reference range. Patient
symptoms may biochemically and clinically improve within 1 week following the
start of therapy.
To note: some patients may have mixed forms of
AIT.
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