Relapse of Graves' disease following development of a pheochromocytoma

Catecholamines stimulate thyroid hormone synthesis as well as release of thyroid hormone and cause immunologic disturbances that possibly contribute to the manifestations of Graves' disease. This has led to repeated speculations about the possible role of catecholamines in the initiation and maintenance of hyperthyroidism. We describe a patient with Graves' disease who was treated with antithyroid drugs for 2 years. After withdrawal of antithyroid drugs, the patient was in remission for 5 years. After the antithyroid drug treatment and the long remission, the probability of relapse of Graves' disease was very low. Nonetheless, a relapse did occur. Two years after subtotal thyroid resection, further investigation because of persistent hypertension revealed a pheochromocytoma. Retrospective anamnestic data suggest that this pheochromocytoma had been present 2 years before the patient's relapse of Graves' disease. This sequence of diseases has not been described previously. The low probability for a Graves' disease relapse in this patient and the association of this patient's relapse with the manifestation of a pheochromocytoma suggest a possible etiologic role of excess catecholamine production in the relapse of Graves' disease.