A 32-year-old man presents to the endocrinology clinic with complaints of progressive joint pain, carpal tunnel syndrome, and coarsening of facial features over the past 5 years. His wife notes that his shoe size has increased from 8 to 11 over this period. On examination, he has prognathism, macroglossia, and enlarged hands with spade-like appearance. Fasting blood glucose is 156 mg/dL. A random serum GH level is 8 ng/mL (normal <2 ng/mL). Oral glucose tolerance test (OGTT) shows failure of GH suppression below 1 ng/mL after 75 g glucose load. MRI pituitary shows a 2.2 cm sellar mass with suprasellar extension. Which of the following is the most appropriate next step in management?