Hypokalemic periodic paralysis is the most common form of periodic
paralysis and is characterized by attacks of muscle
paralysis associated with a low serum
potassium (K+) level due to an acute intracellular shifting. Thyrotoxic periodic
paralysis (TPP), characterized by the triad of muscle
paralysis, acute
hypokalemia, and
hyperthyroidism, is one cause of
hypokalemic periodic paralysis. The triggering of an attack of undiagnosed TPP by β2-adrenergic
bronchodilators has, to our knowledge, not been reported previously. We describe two young men who presented to the emergency department with the sudden onset of muscle
paralysis after administration of inhaled β2-adrenergic
bronchodilators for
asthma. In both cases, the physical examination revealed an enlarged thyroid gland and symmetrical flaccid
paralysis with areflexia of lower extremities.
Hypokalemia with low urine K+ excretion and normal blood
acid-base status was found on laboratory testing, suggestive of an intracellular shift of K+, and the patients' muscle strength recovered at serum K+ concentrations of 3.0 and 3.3 mmol/L. One patient developed
hyperkalemia after a total
potassium chloride supplementation of 110 mmol. Thyroid function testing was diagnostic of
primary hyperthyroidism due to
Graves disease in both cases. These cases illustrate that β2-adrenergic
bronchodilators should be considered a potential precipitant of TPP.