Thyrotoxic periodic paralysis

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Thyroid gland

Periodic paralysis - thyrotoxic

• weakness/paralysis
  • most common in shoulders and hips
  • more common in legs than arms
  • intermittent occurrences
  • 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)
• alert during attacks

Symptoms of hyperthyroidism:

• increased appetite
• weight loss
• skin changes: moist, warm, thin, pale (occasionally)
• tremors
• fast heart rate
• sensation of feeling the heart beat (palpitations)
• headache
• excessive sweating (diaphoresis)
• insomnia
• heat intolerance
• fatigue

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 an enlarged thyroid. During an attack, reflexes may be decreased or absent. Weakness is constant rather than spastic (coming in spasms). The weakness is greater in muscle groups near the body (such as shoulders and hips) than muscle groups farther away from the body (such as arms, hands, legs, or feet). 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:

• low serum TSH (thyroid stimulating hormone) levels
• high thyroid hormone levels (T3 or T4)

Serum potassium is low during attacks but is normal between attacks, confirming the diagnosis. An ECG (electrocardiogram) may be abnormal during attacks. An EMG (electromyogram) is normal between attacks. During an attack EMG is abnormal, showing electrical silence. A muscle biopsy may occasionally show abnormalities.

Review Date: 05/12/2006
Reviewed By: Robert Hurd, MD, Department of Biology, College of Arts and Sciences, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.