Resistant type 2 amiodarone-induced thyrotoxicosis responsive to cholestyramine as an adjunctive therapy

Amiodarone is a class 3 antiarrhythmic drug which may be associated with thyroid dysfunction. Amiodarone-induced thyrotoxicosis (AIT) is classified as type 1 (AIT 1; which may develop in the presence of latent autoimmune hyperthyroid condition) or type 2 (AIT 2; which develops in an apparently normal thyroid resulting from destructive thyroiditis). AIT 1 routinely requires treatment with thionamides, whereas AIT 2 is treated with steroids. Resistance to the conventional treatment of hyperthyroidism is not commonly found in clinical practice. This report discusses a case of AIT 2 resistant to conventional treatment. Despite being on high doses of carbimazole and steroids (prednisolone), the patient remained thyrotoxic. Cholestyramine, a bile salt sequestrant, was used as an adjunctive therapy resulting in significant clinical and biochemical improvement. The patient subsequently became euthyroid and is being followed up in endocrine clinic.