Approach to hypokalemia Quiz: Ace Your Exams

A 26-year-old man presents to the emergency department for evaluation of sudden-onset weakness that started two hours ago. The patient has experienced two similar episodes that each resolved within one hour. However, today, the patient was unable to get out of bed and continued to be weak for 2 1/2 hours, prompting the patient to call an ambulance. The patient has experienced about six months of heat intolerance, palpitations, anxiety, and weight loss. On physical examination, the patient is noted to be thin and diaphoretic. The patient is alert and oriented and appears anxious. The patient’s skin is warm to the touch, and the patient has thinning hair. There is flaccid paralysis of the lower extremities as well as decreased strength in the proximal arms. Distal arm strength is normal without fatigability. Reflexes are diminished throughout. Laboratory studies are notable for a serum potassium of 2.1 mEq/L (reference range: 3.5-5 mEq/L). Which of the following laboratory results would be consistent with the underlying diagnosis?