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Alternative Names Return to topPeriodic paralysis - thyrotoxic
Definition Return to top
Thyrotoxic periodic paralysis is a condition in which there are episodes of muscle weakness in people with high levels of thyroid hormone (hyperthyroidism, thyrotoxicosis).
Causes Return to top
Thyrotoxic periodic paralysis is a rare condition that occurs only in people with high thyroid hormone levels (thyrotoxicosis). It is seen most commonly in Asian men.
There is a similar disorder, hypokalemic periodic paralysis (familial periodic paralysis). This is an inherited condition and does not have high thyroid levels.
Risk factors include a family history of periodic paralysis and hyperthyroidism.
Symptoms Return to top
Thyrotoxic periodic paralysis involves attacks of muscle weakness or paralysis alternating with periods of normal muscle function. Attacks usually begin after symptoms of hyperthyroidism have developed.
The frequency of attacks varies from daily to yearly. Episodes of muscle weakness may last for a few hours or several days.
People are alert during attacks. Normal strength returns between attacks.
Symptoms of hyperthyroidism:
Exams and Tests Return to top
The health care provider may suspect thyrotoxic periodic paralysis based on:
Diagnosis involves ruling out disorders associated with low potassium.
The health care provider may attempt to trigger an attack by giving you insulin and glucose (which reduces potassium levels) or thyroid hormone.
During an attack, there may be the following signs:
Between attacks, examination is normal. Or, there may be signs of hyperthyroidism, such as an enlarged thyroid.
Hyperthyroidism is confirmed by abnormal results on the following tests:
Other test results:
A muscle biopsy may occasionally show abnormalities.
Treatment Return to top
The best treatment is to quickly reduce thyroid hormone levels. Potassium should also be given during the attack, preferably by mouth. If weakness is severe, intravenous potassium may be needed. (Note: intravenous potassium should be given only if kidney function is normal and the patient is monitored in the hospital.)
Weakness that involves the muscles used for breathing or swallowing is an emergency. Patients must be taken to a hospital. Dangerous heart arrhythmias may also occur during attacks.
Your health care provider may recommend that you eat a diet low in carbohydrates and salt to prevent attacks. Medications called beta blockers may reduce the number and severity of attacks while hyperthyroidism is brought under control.
Acetazolamide is effective in preventing attacks in people with familial periodic paralysis. It is usually not effective with thyrotoxic periodic paralysis.
Outlook (Prognosis) Return to top
Chronic attacks will eventually lead to muscle weakness that persists even between attacks. Thyrotoxic periodic paralysis responds well to treatment. Treating hyperthyroidism will prevent attacks and may even reverse muscle weakness.
Possible Complications Return to top
When to Contact a Medical Professional Return to top
Go to the emergency room or call the local emergency number (such as 911) if you have periods of muscle weakness. This is especially important if you have a family history of periodic paralysis or thyroid disorders.
Emergency symptoms include:
Prevention Return to top
Genetic counseling may be advised. Treating the thyroid disorder prevents attacks of weakness.Update Date: 6/17/2008 Updated by: Elizabeth H. Holt, MD, PhD, Assistant Professor of Medicine, Section of Endocrinology and Metabolism, Yale University. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.