Short-term beta-adrenergic blockade decreases serum thyroglobulin in hyper- and euthyroid patients

Cardioselective [Acebutolol (N = 10)] or noncardioselective [Oxprenolol (N = 9)] or [Pindolol (N = 9)] beta-adrenergic blockers were given to patients with suspected hyperthyroidism. Four h after start of the beta blockade median serum thyroglobulin (Tg) had decreased to 33 (range: 13-325) micrograms/l from 41 (range: 12-333) micrograms/l before start in the acebutolol treated group (p less than 0.05). A significant decrease in serum Tg was also found in the oxprenolol-treated group [before start: 45 (24-423) micrograms/l and after 4h: 43 (18-363) micrograms/l (p less than 0.01)] and in the pindolol-treated group [before start: 154 (33-210) micrograms/l and after 4 h: 63 (19-157) micrograms/l (p less than 0.05) treated groups. After 7 days treatment the decrease in serum Tg was significant [to 85 (34-182) micrograms/l (p less than 0.02)] only in the Pindolol-treated group. It is suggested that both hemodynamic changes as well as interference with the intrathyroidal 12 S Tg to 19 S Tg dimerization might explain the changes in serum Tg during beta blockade. Knowledge of drug influence on serum thyroglobulin is important for the interpretation of variations found in patients where thyroglobulin is being used for diagnostic purposes.