Exercise-induced myalgia in hypothyroidism.

Recurrent rhabdomyolysis is very uncommon in hypothyroid myopathy. A 30-year-old woman is reported, who presented with exercise-induced myalgias and high levels of serum creatine kinase but no muscle weakness. Muscle biopsy showed signs of a recurrent rhabdomyolysis. Hypothyroidism was diagnosed by serum hormone levels. The myopathy rapidly improved with thyroxine treatment.