The effect of propranolol on thyroid hormones in T3 toxicosis.

Serum thyroid hormone concentrations were measured before and during 6 months treatment with propranolol (160 mg/day) in eight patients with T3 (triiodothyronine) toxicosis. Serum total T3 concentrations showed a significant (p less than 0.01) and sustained fall to approximately 80% of pre-treatment values. Six of the patients, however, remained clinically and biochemically hyperthyroid and our data do not support the use of propranolol as sole therapy in T3 toxicosis.