You are answering a USMLE-style medical question. Question: A 14-year-old teenager presents to his pediatrician complaining of frequent headaches and excessive fatigue during soccer practice. His mother notes that he seems to have gained a lot of weight despite the fact that he eats a healthy, well-balanced diet. His teachers have also become concerned because he leaves class to use the restroom frequently throughout the day. He has no medical problems and family history is insignificant. A physical exam is significant for a short, overweight child with nonpitting edema and decreased reflexes. His systolic blood pressure drops by 20 mm Hg when he stands. Fundoscopic exam is significant for papilledema and visual field exam is significant for bitemporal hemianopsia. Laboratory findings include: BUN 22 mg/dL N: 7–20 mg/dL pCO2 32 mm Hg N: 35–45 mm Hg Creatinine 0.8 mg/dL N: 0.8–1.4 mg/dL Glucose 50 mg/dL N: 64–128 mg/dL Serum chloride 95 mmol/L N: 101–111 mmol/L Serum potassium 3.3 mEq/L N: 3.7–5.2 mEq/L Serum sodium 120 mEq/L N: 136–144 mEq/L Bicarbonate (HCO3) 15 mmol/L N: 18–22 mmol/L Thyroid-stimulating hormone (TSH) 0.1 mIU/L N: 0.5–5 mIU/L Free T4 6 pmol/L N: 10–20 pmol/L What is the necessary treatment? Options: A) Chemotherapy, surgical resection and radiation B) Chemotherapy and radiation C) Surgical resection D) Hormone replacement therapy Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.