[The effect of arotinolol on the thyroid function and the autonomic nerve systems]

beta-blockers have been accepted as a reasonable adjunct therapy for the treatment of hyperthyroidism. They lessen the sympathetic symptoms such as tachycardia and finger tremor. On the other hand, many studies have demonstrated a decrease in 3, 3', 5-triiodothyronine (T3) during treatment with beta-blockers (especially propranolol). The purpose of this study is to clarify the effect of arotinolol (alpha 1, beta-blocker) on the thyroid functions and autonomic nerve systems (ANS) of patients with Graves' disease. Arotinolol 20mg a day p.o. was given to untreated patients with Graves' disease (n = 16) for 2 weeks. Blood sampling and the ANS function-tests were done before and after the treatment. In addition, the in vitro effects of arotinolol on the cAMP production and the radioactive iodine uptake (RAIU) using rat thyroid cell line FRTL5 were evaluated to examine the direct influence on thyroid cells. Arotinolol improved hyperthyroid symptoms including tachycardia, but had no effect on ANS function-tests. It is of interest that not only T3 but also T4 decreased after the arotinolol treatment. We therefore suspected the direct suppressive effects of arotinolol on the thyroid. There were, however, no in vitro inhibitory effects on the cAMP production and the RAIU in TSH-stimulated FRTL5 cells. The reason why serum T4 levels in patients with untreated Graves' disease have decreased after the treatment of arotinolol could not be clarified. In conclusion, arotinolol is a very useful drug for the initial therapy of patients with Graves' disease to reduce the serum thyroid hormone levels and symptoms of hyperthyroidism when combined with antithyroid drugs.