A 32-year-old female patient arrives for follow-up for new-onset hypertension. She was started on hydrochlorothiazide 6 months ago. During her visit, she was found to have a blood pressure of 152/ 98 mmHg. She also complains of recent episodes where she experiences sudden palpitations, chest pain, diaphoresis, headache, and anxiety. Her laboratory exam demonstrates a calcium of 13.2 mg/ dl (normal 8.5- 10.2 mg/ dl), PTH of 102 pg/ ml (10- 55 pg/ ml), and an elevated plasma metanephrine. Which of the following would be an important additional component in the workup?
(A) Fasting blood glucose
(B) Prolactin level
(C) MRI of the sella turcica
(D) Serum calcitonin
(E) Serum gastrin level