Thyrotoxic myopathy is a neuromuscular disorder that may accompany hyperthyroidism (Graves’ disease, caused by overproduction of the thyroid hormone thyroxine). Symptoms may include muscle weakness, myalgias (muscle tenderness), wasting of the pelvic girdle and shoulder muscles, fatigue, and/or heat intolerance.
Thyroid myopathy may be associated with rhabdomyolysis (acute muscle breakdown), damage to the muscles that control eye movement, and temporary, but severe, attacks of muscle weakness that are associated with low blood potassium levels (known as periodic paralysis).
With treatment, muscle weakness may improve or be reversed.
Treatment involves restoring normal levels of thyroid hormone and may include thyroid drugs, radioactive iodine, and sometimes partial or complete surgical removal of the thyroid.