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Thyrotoxic periodic paralysis Causes and Risks:
Hypokalemic periodic paralysis ( familial periodic paralysis ) is an inherited condition, and in most cases, it is directly inherited. In other cases, the disorder appears sporadically in a family group. It can occur in people with thyrotoxicosis (high thyroid hormone levels ), especially when the condition has persisted for several months. About 10% of people with hyperthyroidism will exhibit thyrotoxic periodic paralysis. The disorder is most common in men, particularly Latin American and Asian men.
The disorder 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 may persist for several days.
During an attack, there is a low level of potassium in the bloodstream (serum). Serum potassium levels are normal between attacks. There is no decrease in total body potassium, however. Potassium flows from the bloodstream into muscle cells. Insulin levels may affect the disorder in some people because insulin increases the flow of potassium into cells.
Weakness most commonly affects the muscles of the arms and legs. It may occasionally affect the muscles of the eyes or the muscles involved in breathing and swallowing (which can be fatal). Heart arrhythmias may occur during attacks because of the drop in potassium levels. Although muscle strength is initially normal between attacks, repeated attacks may eventually cause progressive and persistent muscle weakness.
Risks include a family history of periodic paralysis and hyperthyroidism. Attacks may be triggered by eating high carbohydrate or high salt meals or by taking a thyroid hormone. Attacks most commonly occur after sleep or rest and are rare during exercise , but rest after an exercise period may trigger an attack.
Prevention:
Genetic counseling may be advised. Treatment of the underlying thyroid disorder prevents attacks of weakness .
Symptoms:
- weakness / paralysis
- shoulders and hips are the most common location
- arms and legs may possibly be involved
- intermittent occurrences
- most commonly occurring upon awakening
- triggered by rest after exercise
- triggered by heavy, high carbohydrate , high salt meals
- lasting for up to several days
- spontaneous recovery of normal strength between attacks
- vision changes (rare)
- swallowing difficulty (rare)
- speech difficulty (rare)
- difficulty breathing (rare)
- person is alert during attacks
Symptoms of hyperthyroidism :
Signs and Tests:
The health care provider may suspect thyrotoxic periodic paralysis based on a family history of the disorder, the episodic nature of symptoms, low potassium levels during attacks, abnormal thyroid hormone levels , and elimination of other disorders associated with low potassium as the cause of symptoms.
Between attacks, examination is normal, or there may be signs of hyperthyroidism , such as a palpably enlarged thyroid. During an attack, reflexes may be decreased or absent. Weakness is constant rather than spastic (spasmodic) and is greater in proximal muscle groups (near the body, such as the shoulders or hips) than in distal groups (away from the body, such as the arms or legs). The health care provider may attempt to trigger an attack by administering insulin and glucose (which reduces potassium levels) or thyroid hormone.
Hyperthyroidism is confirmed by abnormal results of: - TSH levels
- T3
- T3 resin uptake
- T4
- Serum potassium is low during attacks but is normal between attacks, confirming the diagnosis.
- An ECG may be abnormal during attacks.
- An EMG is normal between attacks; during an attack EMG is abnormal, showing electrical silence.
- A muscle biopsy may occasionally show abnormalities.
Treatment:
The goals of treatment are relief of acute symptoms and prevention of further attacks. Weakness that involves the muscles used for breathing or swallowing is an emergency situation. Dangerous heart arrhythmias may also occur during attacks.
Potassium that is given during an attack may stop the attack. It is preferred that potassium be given by mouth, but if weakness is severe, intravenous potassium may be necessary. (Note: intravenous potassium should be given only if kidney function is adequate and if the person is monitored in the hospital.)
A diet that is low in carbohydrates and salt may be recommended.
Treatment of the underlying thyroid disorder usually stops attacks.
Beta-blockers may reduce the number and severity of attacks while measures to control hyperthyroidism are occurring.
Acetazolamide, a medications that is effective in attack prevention with familial periodic paralysis , is often ineffective with thyrotoxic periodic paralysis.
Prognosis:
Chronic attacks will eventually result in progressive muscle weakness that is present even between attacks. Thyrotoxic periodic paralysis responds well to treatment. Treatment of hyperthyroidism may prevent and may even reverse progressive muscle weakness.
Complications:
Call Your Healthcare Provider:
Go to the emergency room or call the local emergency number (such as 911) if intermittent muscle weakness occurs, particularly if there is a family history of periodic paralysis or thyroid disorders . Fainting , and difficulty breathing , speaking, or swallowing are among the emergency symptoms.
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