A Case of Recurrent Paralysis and Low Potassium: Is It the Thyroid?

Introduction: Thyrotoxic periodic paralysis (TPP) is a rare complication of hyperthyroidism that is characterized by episodes of hypokalemia and acute weakness. Although hyperthyroidism is more common in females, over 95% of cases of TPP have been observed in males, especially in Asian males with an incidence of 2% among hyperthyroid patients. In non-Asian populations, the incidence in hyperthyroid patients is estimated to be around 0.1 to 0.2% [1]. We describe a case of TPP seen in a Hispanic male. Case Report: A 36-year-old Hispanic male with no past medical history presents with weakness in all extremities and difficulty breathing after consuming a carbohydrate heavy meal the night prior. He reports a recent, similar episode evaluated in another ER, which resolved after given potassium supplementation. He denied any vomiting, diarrhea, polyuria, diaphoresis, use of insulin or other medications, or any family history of paralysis. His labs were significant for hypokalemia of 1.9, TSH of <0.005 (0.358-3.740), free T4 of 2.22 (0.76-1.46), and total T3 of 2.7 (0.60-1.81). Thyroid stimulating immunoglobulin was 0.12 (0.0-0.55). His symptoms improved and potassium levels normalized following the administration of potassium chloride. He was discharged on propranolol and advised to follow up for further workup of his hyperthyroidism with radioactive iodine uptake scan. Discussion: Thyrotoxic periodic paralysis is a potentially life-threatening condition associated with cardiac arrhythmias and respiratory failure. Hyperthyroidism increases response to β-adrenergic stimulation, which increases activity of the sodium-potassium ATPase and causes hyperpolarization of skeletal muscle [2]. Hyperthyroid patients are prone to episodes of paralysis due to their increased susceptibility to the hypokalemic action of insulin, which activates the sodium-potassium ATPase pump, and epinephrine, which stimulates β-adrenoreceptors. Management of an acute attack of TPP includes potassium administration. In cases where paralysis and hypokalemia are not reversed, intravenous propranolol has been shown to resolve the attack by blocking the β-adrenergic receptors. Definitive treatment of TPP includes managing the hyperthyroid state with medical therapy, radioactive iodine therapy, or surgery. Until the euthyroid state is reached, a β-blocker can prevent episodes of acute paralysis. Avoidance of carbohydrate heavy meals, exercise, and stress are recommended as these factors can potentially exacerbate hypokalemia. In patient with acute paralysis, it is important to consider the diagnosis of TPP as this condition can be prevented once euthyroidism is achieved. Diagnosis and management will lead to prevention of morbidity and mortality associated with the hypokalemia. References: 1.Vijayakumar A, et al. J Thyroid Res. 2014;2014:649502. 2.Layzer RB. Annals of Neurology. 1982;11(6):547–552.