Effect of carteolol, indenolol and metoprolol on the thyroid hormone of hyperthyroid patients.

Abstract

----Thirty-four hyperthyroid patients were divided into four groups : placebo, carteolol (20 mg/day), indenolol (60 mg/day) and metoprolol (120 mg/day) groups. The heart rate was determined before and two weeks after the treatment with each drug. Serum levels of T4, T3 and rT3 were measured before, and one and two weeks after the treatment. Both indenolol and metoprolol significantly reduced the heart rate (p <0.01 and p <0.05, respectively), whereas carteolol was ineffective. Carteolol significantly decreased T4 from 23.4± 4.4 ,u g/ 100 ml to 20.1 + 3.2,u g/ 100 ml (p < 0.01) in one week and to 20.0±3.7,ug/100 ml (p <0.01) in two weeks. T3 and rT3 were also decreased significantly (p <0.05 and p <0.01, respectively) two weeks after the treatment with carteolol. After two weeks of indenolol treatment, T4 was decreased significantly from 26.2±8.5 u g/ 100 ml to 23.9±8.2 p g/100 ml (p < 0.05) and T3 from 789+391ng/100 ml to 592+340 ng/100 ml (p <0.02). Metoprolol had no effect on serum thyroid hormone levels. The decrease in the serum level of thyroid hormones by carteolol and indenolol but not by metoprolol in patients with hyperthyroidism would be due to the blockade of f2-adrenoreceptors concerning with thyroid hormone secretion.carteolol; indenolol ; metoprolol ; thyroid hormone ; hyperthyroidism Propranolol causes a fall in serum triiodothyronine (T3) concentration in hyperthyroid patients (Verhoeven et al. 1977 ;Kallner et al. 1978 ;Saunders et al. 1978), probably by its action on peripheral conversion of thyroxine (T4) to T3 and reverse T3 (rT3) (Heyma et al. 1980;Nilsson et al. 1980), although f3-adrenoreceptor blockers other than propranolol were reported to have no effect on serum thyroid hormones (Murchison et al. 1976;Wahlberg et al. 1976;Nilsson et al. 1979: Jones et al. 1981.