Reducing effect of nadolol on serum levels of free thyroid hormones in hyperthyroidism

We evaluated the effect of the beta-adrenergic receptor blocking agent nadolol on serum levels of free thyroid hormones in 20 untreated patients with Graves' disease, aged between 17 and 57 years (mean +/- SD, 32.9 +/- 10.5). All the patients were treated with 30 mg of nadolol alone once-daily for 2 weeks, and clinical and laboratory parameters before and after the treatment were compared. Systolic blood pressure was depressed significantly (P < 0.001) from 132.7 +/- 11.1 mmHg to 122.8 +/- 10.9 mmHg. The resting pulse rate was also reduced significantly (from 110.3 +/- 9.2/min to 86.0 +/- 13.2/min, P < 0.001). Serum free thyroxine levels were reduced significantly from 7.1 +/- 3.1 ng/dl to 5.7 +/- 3.6 ng/dl (P < 0.05) and serum free triiodothyronine levels were reduced from 21.9 +/- 5.6 pg/ml to 17.2 +/- 6.9 pg/ml (P < 0.01). In the present study, the beta-adrenergic receptor blocking agent nadolol was newly found to have a reducing effect on serum free thyroxine, as well as free triiodothyronine concentrations.