Thyrotoxic periodic paralysis is a condition in which there are episodes of muscle weakness in people who have high levels of thyroid hormone in their blood (hyperthyroidism, thyrotoxicosis).
Periodic paralysis - thyrotoxic
Causes, incidence, and risk factors
Thyrotoxic periodic paralysis is a rare condition that occurs only in people with high thyroid hormone levels (thyrotoxicosis). It is most commonly seen in Asian men.
There is a similar disorder, called hypokalemic periodic paralysis (familial periodic paralysis). This is an inherited condition and is not related to high thyroid levels.
Risk factors include a family history of periodic paralysis and hyperthyroidism.
Thyrotoxic periodic paralysis involves attacks of muscle weakness or paralysis that alternate with periods of normal muscle function. Attacks usually begin after symptoms of hyperthyroidism have developed.
How often attacks can occur varies from daily to yearly. Episodes of muscle weakness may last for a few hours or several days.
Low potassium in the bloodstream (serum potassium levels are normal between attacks)
Weakness, especially in the muscles of the arms and legs and occasionally in the muscles of the eyes. The muscles involved in breathing and swallowing can sometimes be affected, and this can be fatal. Muscle strength is normal between attacks at first. However, repeated attacks may eventually cause worsening and persistent muscle weakness.
Between attacks, the examination is normal. Or, there may be signs of hyperthyroidism, such as an enlarged thyroid.
The following tests are used to diagnose hyperthyroidism:
The best treatment is to quickly reduce thyroid hormone levels. Potassium should also be given during the attack, usually by mouth. If weakness is severe, you may need to get potassium through a vein (intravenously). (Note: You should only get intravenous potassium if kidney function is normal and you are 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 your hyperthyroidism is brought under control.
Acetazolamide is effective at preventing attacks in people with familial periodic paralysis. It is usually not effective for thyrotoxic periodic paralysis.
Chronic attacks will eventually lead to muscle weakness that continues even between attacks.
Thyrotoxic periodic paralysis responds well to treatment. Treating hyperthyroidism will prevent attacks and may even reverse muscle weakness.
Difficulty breathing, speaking, or swallowing during attacks (rare)
Heart arrhythmias during attacks
Muscle weakness that gets worse over time
Calling your health care provider
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:
Difficulty breathing, speaking, or swallowing
Genetic counseling may be advised. Treating the thyroid disorder prevents attacks of weakness.
Shehzad Topiwala, MD, Chief Consultant Endocrinologist, Premier Medical Associates, The Villages, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.