Hyperthyroidism after propranolol withdrawal.

Classic features of thyrotoxicosis developed in three patients with no prior history of thyroid disease shortly after the discontinuation of therapy with or decrease in doseage of propranolol hydrochloride. Graves' disease probably developed fortuitously after propranolol therapy was instituted, but the beta-adrenergic blockade masked the clinical features of hyperthyroidism. On discontinuation of propranolol therapy or decrease in propranolol dosage, previously latent thyrotoxicosis became manifest. If hyperthyroidism masked by beta-blockade is not recognized before withdrawal of propranolol therapy in patients with ischemic heart disease, the sudden appearance of thyrotoxicosis may lead to symptoms of increased myocardial ischemia.