The effect of atenolol on serum thyroid hormones in hyperthyroid patients.

The effect of the beta-1-adrenoceptor blocking agent, atenolol, on serum levels of thyroxine (T4), triiodothyronine (T3) and reverse triiodothyronine (rT3) was studied in twelve hyperthyroid patients. While all patients improved symptomatically after treatment with atenolol 100 mg twice daily for 2 weeks, there were no significant changes in the serum T3 or rT3 concentrations. The serum T4 level showed a small but statistically significant fall. These data do not support the hypothesis that the beneficial clinical effects of beta-adrenoceptor blocking drugs in thyrotoxicosis are mediated by an action on the peripheral metabolism of thyroid hormones.