Background: Resistance to the conventional treatment of hyperthyroidism with antithyroid drugs is not commonly found in clinical practice, and only few other treatment options have been reported on in detail. For example, surgery or radioiodine ablation are well-accepted interventions that must be always considered. The euthyroid state is strongly recommended before both of these as this might reduce complications. There are few studies indicating that bile acid sequestrants, when added to antithyroid drugs, produce a more rapid decline in serum thyroid hormone levels and that this effect is maintained for at least 4 weeks. Complete normalization of serum thyroid hormone levels is generally not expected, however.
Summary: We report a patient whose thyrotoxicosis failed to respond to conventional treatment. The patient remained persistently hyperthyroid, both clinically and biochemically, despite several months of methimazole and propranolol and the addition of iodine. Cholestyramine, a bile acid sequestrant, was then added, and a dramatic improvement was observed.
Conclusion: We report a patient who was resistant to conventional antithyroid drugs in whom thyroid hormone levels completely normalized after 1 week of additional treatment with cholestyramine.