INFORMATION ON THYROTOXIC MYOPATHY

Thyrotoxic myopathy is a neuromuscular disorder that occurs due to overproduction of thyroid hormone and is characterized by excessive fatigability, muscle wasting and weakness. It mainly affects muscles of the shoulder, hips and hands. The adverse effects of thyroid hormone on the structure and function of muscles gives rise to this myopathy. 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. Thyrotoxic myopathies have other names like hyperthyroid myopathy, Graves and Basedow's myopathy or Basedow paraplegia. It was first recognized in the early nineteenth century by Graves and Von Basedow as occurring infrequently in severe hyperthyroidism. In the middle of the twentieth century, researchers found that up to 80% of hyperthyroid patients manifested at least some degree of muscle weakness and this was confirmed on electromyographic studies.

SYNONYMS OF THYROTOXIC MYOPATHY

Synonyms and related keywords:

1. Myopathy - Thyrotoxic.
2. Endocrine myopathy.
3. Adrenal dysfunction.
4. Cushing syndrome.
5. Steroid myopathy.
6. Thyroid dysfunction.
7. Multiple endocrine neoplasia.

CAUSES OF THYROTOXIC MYOPATHY

Thyrotoxic myopathy can occur due to several causes. Of these, only two are commonly associated with myopathy.
1 One of them is multinodular goiter, when the thyroid gland becomes studded with nodules, enlarges and overproduces thyroxine.
2 The other is Graves’s disease, where the body launches an autoimmune attack on the thyroid gland and causes it to produce excess thyroxine.
3 The disease doesn't cause any muscle wasting; instead, it can sometimes cause muscle enlargement and increased muscle strength.
4 Graves disease, caused by overproduction of the thyroid hormone thyroxine.

SYMPTOMS OF THYROTOXIC MYOPATHY

Symptoms for Thyrotoxic Myopathy includes:

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. The stiffness can interfere with simple activities like walking, grasping and chewing, but is usually manageable by doing warm-up movements.

DIAGNOSIS OF THYROTOXIC MYOPATHY

The diagnosis is clinical and is usually made by a neurologist who has expertise in neuromuscular disorders. There should be a high index of clinical suspicion as the pattern of muscle weakness is nonspecific and often patients do not know that they are hyperthyroid. Blood tests show an elevated thyroxine level. In Graves’s disease, antibodies against the thyroid gland are present. CT scans or MRI scans can be used to see the swollen eye muscles.

TREATMENT OF THYROTOXIC MYOPATHY

Thyrotoxic Myopathy is fortunately reversible provided the underlying hyperthyroidism is corrected and a normal thyroid state is restored. This can be done with medications, radiation, or surgery. Treatment is also aimed at symptomatic relief, prevention, and treatment of complications. 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.