PLE-2150

PLE-2150

A 26-year-old woman is brought to the emergency department because of marked confusion for 2 hours. She also has had a flu-like illness for 3 days. Over the past 6 weeks, she has had increased fatigue, weakness, and nausea. She recently started thyroid hormone replacement therapy for autoimmune thyroiditis. 1 week ago, her serum thyroid stimulating hormone level was 3µU/mL. Her temperature is 38 C (100.4 F), blood pressure is 80/40 mm Hg, and pulse is 140/min. She appears confused and lethargic. Examination shows cool, mottled skin. There is generalized hyperpigmentation, especially involving the palmar creases. The lungs are clear to auscultation. Abdominal examination shows diffuse mild tenderness and no rebound. Laboratory studies show: Hemoglobin 10 g/dL, leukocyte count 9000/mm3, segmented neutrophils 55%, eosinophils 20%, lymphocytes 25%. Serum: Na+ 124 mEq/L, Cl- 92 mEq/L, K+ 6.4 mEq/L, HCO3- 16 mEq/L. An x-ray film of the chest and urinalysis show normal findings. An ECG shows sinus tachycardia with peaked T waves. Which of the following is most likely to confirm the primary cause of this patient’s condition?