Relapse of Graves' disease in a patient with pheochromocytoma

We describe a patient with right adrenal tumor detected incidentally. The tumor was diagnosed as pheochromocytoma by endocrinological and radiological studies, and was removed surgically. Graves' disease, which had been in remission for more than two decades after discontinuation of antithyroid drug treatment, relapsed during preoperative evaluation of pheochromocytoma when the patient was treated with alpha- and beta1-adrenergic antagonists. Administration of methimazole resulted in a rapid improvement of thyroid function and the patient remained euthyroid on small doses of methimazole. This case may suggest possible involvement of excessive catecholamine secretion and beta2-adrenergic receptor activation by pheochromocytoma in the relapse of Graves' disease.