Compared effect of propranolol and acebutolol on serum thyroid hormones' levels in euthyroid and hyperthyroid...

An open randomized study involving 57 subjects, 40 euthyroid and 17 hyperthyreotic, was undertaken to compare the effect of two beta-adrenergic blocking drugs, propranolol (120 mg/day) and acebutolol (600 mg/day), on the thyroid hormones serum level. In hyperthyreotic as well as in euthyroid subjects, propranolol evoked a fall in T3, an increase in reverse T3 and therefore a decrease in the T3/rT3 ratio. Acebutolol caused a decrease in T3 and in the T3/rT3 ratio only in euthyroid subjects. The only significant variation in the hyperthyroid acebutolol treated group was a decrease in reverse T3, perhaps spontaneous. TBG and TSH concentrations remained stable under treatment in all the groups. The relation of these effects with the existence of a membrane stabilizing activity displayed by propranolol as well as by acebutolol is discussed.