A tall, thin, 25-year-old woman presents to the surgical clinic with a complaint of swelling in the front of her neck for the last four months. On clinical examination she has a swelling in the left lobe of the thyroid and multiple neuromatous lesions within the oral cavity. Her blood pressure is 220/120 mmHg. Laboratory investigations show that her calcium and electrolytes are normal and serum calcitonin and urinary VMA levels are elevated. Which of the following is the most likely cause of the hypertension?