<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 43-year-old male with a history of thyroid cancer status post total thyroidectomy presents to his primary care physician after repeated bouts of headaches. His headaches are preceded by periods of anxiety, palpitations, and sweating. The patient says he is unable to pinpoint any precipitating factors and instead says the events occur without warning. Of note, the patients father and uncle also have a history of thyroid cancer. On exam his vitals are: T 36.8 HR 87, BP 13593, RR 14, and O2 Sat 100 on room air. The patients TSH is within normal limits, and he reports taking his levothyroxine as prescribed. What is the next best step in diagnosing this patients chief complaint?? A: Abdominal CT scan with and without IV contrast, B: 24-hour urine free cortisol, C: High dose dexamethasone suppression test, D: Plasma fractionated metanephrines, E: Plasma aldosteronerenin ratio,  <response>: This is a question about diagnosing a patient with a history of thyroid cancer who is presenting with recurrent headaches, anxiety, palpitations, and sweating. The key details in the stem are the patients personal and family history of thyroid cancer, his normal TSH level despite taking levothyroxine, and the paroxysmal symptoms he is experiencing. The symptoms of headaches, palpitations, sweating, and anxiety are concerning for an episodic catecholamine excess state such as pheochromocytoma. This is further supported by his family history of thyroid cancer, as pheochromocytoma can be associated with genetic syndromes like MEN 2 that also predispose to thyroid cancer. Choices A and B can be eliminated, as an abdominal CT or urine cortisol would not help diagnose his current symptoms. Choice C, a high dose dexamethasone suppression test, could help rule out Cushings syndrome but would not be the best test here. Choice E, checking an aldosteronerenin ratio, could evaluate for primary aldosteronism but again does not fit with his symptomatology. Choice D, checking plasma fractionated metanephrines, is the best next step as this is the most sensitive test for diagnosing pheochromocytoma. This allows measurement of plasma levels of norepinephrine and metabolites like normetanephrine which are typically elevated in pheochromocytoma patients.D: Plasma fractionated metanephrines 