You’re called to take care of the United States President John F.Kennedy. The President informs you that he has been suffering from nausea and fatigue that started while he was outside playing tennis. On further questioning, he reports a gradual onset of weakness, lethargy, and easy fatigability over the last four months. Two days ago he experienced a near-fainting spell while walking to Air Force One. The review of systems reveals abdominal pain, weight loss and chronic diarrhea. His family history is significant for Hashimoto thyroiditis and rheumatoid arthritis. On examination, his temperature is 99.6 °F, heart rate is 92 beats per minute, blood pressure 98/68 mm Hg and respiratory rate is 16 breaths per minute. He is alert and oriented. His pulses are rapid and thready. There is calcification of auricular cartilage in both ears. His lungs are clear and his heart rhythm becomes tachycardic after standing but regular. He has normal bowel sounds and mild diffuse tenderness without guarding. Skin has hyperpigmented regions over his neck, knuckles, knees, and elbows. Laboratory studies are given below: Lab test Patient result Reference Sodium 119 mEq/L 136 – 146 mEq/L Potassium 5.9 mEq/L 3.5 – 5.0 mEq/L Chloride 92 mEq/L 95 – 105 mEq/L Bicarbonate 16 22 – 28 mEq/L Glucose 55 mEq/L 70 – 100 mEq/L Cortisol 0800 hr: 2 micrograms/dL 0800 h: 5-23 micrograms/dL The President enquires you about the most likely causes of his disorder. Which of the following is the most common cause of this disorder in the United States?
