Thyrotoxicosis

To the Editor.  —I recently saw a woman with thyrotoxicosis treated with methimazole and pindolol in whom severe myalgia developed associated with a markedly elevated level of serum creatine phosphokinase (SCPK). Although it has been identified that propranolol hydrochloride might cause myopathy and elevation of SCPK,¹ it has not been well defined whether pindolol may induce clinically manifest myopathy.²

Report of a Case.  —A 29-year-old woman visited our hospital in October 1981 because of a ten-month history of goiter, tachycardia, and amenorrhea. The diffuse goiter was three times enlarged. Triiodothyronine (T₃) and thyroxine levels by radioimmunoassay and T₃ resin uptake showed substantial elevations to 5.5 ng/mL, 12.9 μg/dL, and 48.5%, respectively. The level of thyroid-stimulating hormone was 1.25 μU/mL. The antithyroglobulin test result was negative, but an antimicrosome test result was clearly positive at 1:6,400. The SCPK level was 39 U/mL.During a four-week interval, the