A Case of Hyperthyroid Myopathy Due to Graves' Disease

A 49-year-old woman was admitted with a three-month history of myalgia and progressive proximal and distal muscle weaknesses. Physical examination showed diffuse enlargement of the thyroid gland and mild muscle atrophy. Serum creatine kinase was slightly increased and electromyography showed a myopathic pattern. Muscle biopsy showed nonspecific myopathic changes. Serum thyroid-stimulating hormone was very low, whereas thyroxine (T4) was greatly increased as well as anti-thyroglobulin, anti-microsome, and TSH-receptor antibody. The patient's symptoms were improved during the treatment with propilthiouracil.