[Thyroid function and amiodarone. Consequences on dysthyroidism testing].

Amiodarone induces a decrease in serum T3 whereas T4 and rT3 increase. An increase of the thyroid iodine content (TIC) is observed in all patients at the exception of those who develop hypothyroidism under treatment. Actually, no method are available to predict an induced thyroid toxicosis (ITT) and there is no reason to perform systematically thyroid function tests except if past of the patient or clinical or morphological thyroid examinations suggest thyroid abnormality. In case of suspicion of ITT it is necessary to perform T4, T3 determinations and a TRH test. TIC measurement can be useful in order to eliminate a subacute or silent thyroiditis. Hypothyroidism is generally observed in patients with autoimmune thyroiditis. Antithyroid antibodies and TSH determinations after some months of treatment can detect subclinical hypothyroidism which is due to a high susceptibility to iodide.