ABSTRACT
Thyrotoxic periodic paralysis is a life-threatening complication characterized by acute paralysis of proximal muscles with severe hypokalemia in patients with a known or undiagnosed history of thyrotoxicosis. A 24-year-old man was brought to the emergency room with 1 month of progressively worsening lower-extremity weakness followed by urinary retention. He demonstrated severe motor weakness in proximal muscles with absent reflexes. Laboratory testing showed a dangerously low potassium of 1.3 mmol/L. Further testing to establish an etiology revealed a new diagnosis of thyrotoxicosis, and the patient was also started on the antithyroid medication methimazole and propranolol. Immediate oral and intravenous potassium supplementation was initiated to normalize the serum potassium levels to 4.7 mmol/L; that was followed by the gradual recovery of his motor function. This case report highlights the need for early consideration of endocrine and metabolic causes of acute flaccid paralysis.