What is Thyrotoxic Myopathy?

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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, wasting of the pelvic girdle and shoulder muscles, fatigue, and heat intolerance. Muscle breakdown may occur in acute cases. Physical acts such as climbing stairs may be difficult. Patients may develop muscle damage to the eyes and eyelids, which may affect mobility of the eye muscles, and temporary, but severe, attacks of muscle weakness known as periodic paralysis.

Is there any treatment?
Treatment is based on treatment for hyperthyroidism and may include prescription of iodine and other drugs, beta-blockers, and surgery. Myopathy may improve by restoring normal thyroid function. Complete or partial removal of the thyroid may be required in severe cases.

What is the prognosis?
With treatment, muscle weakness may improve or be reversed.

What research is being done?
The NINDS supports a broad range of research on neuromuscular disorders such as thyrotoxic myopathy. Much of this research is aimed at learning more about these disorders and finding ways to prevent and treat them.

Synonyms: Myopathy - Thyrotoxic