A 26-year-old male presents with: weakness, an 18-pound weight loss, a change in the color of his skin and
lightheadedness and dizziness. PE: skin hyperpigmentation since you last saw him 6-months ago. BP is 90/ 70
mm Hg. He looks acutely ill. Labs: serum sodium is low (115 mEq/ L), his serum potassium is high (6.2 mEq/ L),
his serum urea is elevated at 9 mg/ dL, and his serum calcium is elevated (12 mg/ dL). What is the most likely
cause?