Hypothyroid myopathy with unusually high serum creatine kinase values

Depending on the degree of hormone deficiency, skeletal muscle involvement may occur in hypothyroidism. Usually, hypothyroid myopathy is associated with creatine kinase values <5,000 U/l. We report a 54-year-old man suffering from increasing fatigability, hoarseness, gait disturbances and a creatine kinase of 9,000 (normal: <80 U/l). He presented with bradyphrenia, macroglossia, dysarthria, myxedema, monoparesis, reduced deep tendon reflexes and stocking-type sensory disturbances. Free triiodthyronine was 0.25 pg/ml (normal: 0.6-1.9 pg/ml), free thyroxine <0.1 ng/dl (normal: 0. 6-1.8 ng/dl) and the thyroid-stimulating hormone >48.0 (normal: 0. 1-4.0 IU). Clinical neurologic examination and electromyography were compatible with myopathy and polyneuropathy. Other causes of myopathy, except hypothyroidism, were excluded. After L-thyroxine therapy (1.7 microg/kg BW/day) during 3 months, the patient's symptoms and signs vanished, except for sensory disturbances, and creatine kinase values and electromyography became normal. Severe hypothyroidism may be associated with highly elevated creatine kinase and myopathy. Adequate therapy leads to complete recovery, including myopathy.