Review Question - QID 214888

This patient presents with episodic hypertension, headache, tachycardia, diaphoresis, and hyperglycemia which is most consistent with a pheochromocytoma. The initial step in management is plasma free metanephrines.

Pheochromocytomas are tumors of the adrenal medulla that intermittently secrete catecholamines such as epinephrine and norepinephrine which bind α- and β-adrenergic receptors and cause a sympathetic surge. Patients can present with paroxysmal episodes of hypertension, headache, tachycardia, diaphoresis, hyperglycemia, and anxiety. Elevated plasma free metanephrines (a breakdown product of catecholamines) are the most appropriate initial test. Confirmatory tests include 24-hour urine metanephrines or vanillylmandelic acid (another breakdown product of catecholamines). Alpha blockade with phenoxybenzamine followed by tumor resection is the definitive treatment. Pheochromocytomas are often found in patients with neurofibromatosis type 1, von Hippel-Lindau disease, and multiple endocrine neoplasia (MEN) 2A and 2B.

Bancos et al. study maternal and fetal outcomes of pheochromocytoma in pregnancy. The authors found that alpha-adrenergic blockade therapy was associated with better outcomes during pregnancy; however, surgery during pregnancy was not associated with better outcomes. The authors recommend prompt diagnosis and treatment of pheochromocytoma during pregnancy.

Incorrect Answers:
Answer 1: 24-hour urine free cortisol is used to evaluate for Cushing syndrome, which can manifest as hypertension, elevated blood glucose, central obesity, muscle wasting, and purple striae. The sudden rise in blood pressure and blood glucose in this patient is due to the episodic release of catecholamines, not cortisol.

Answer 3: Renal Doppler ultrasound can be used to evaluate hypertension from renal artery stenosis (RAS). RAS typically presents with persistent hypertension that is refractory to multiple antihypertensive agents, and not brief episodes of hypertension as in this patient.

Answer 4: The renin-to-aldosterone ratio helps differentiate hypertension from RAS (both renin and aldosterone elevated) and aldosteronoma (low renin and high aldosterone). Both conditions cause non-episodic, medication-refractory hypertension with no associated hyperglycemia.

Answer 5: Repeat blood pressure at the next visit is an appropriate next step for confirming a new diagnosis of uncomplicated essential hypertension, which presents as an asymptomatic elevation in blood pressure without an identifiable cause. This would delay the workup for a suspected pheochromocytoma and increase the risk of a hypertensive crisis, a feared complication.

Bullet Summary:
The most appropriate initial diagnostic test in pheochromocytoma is the measurement of plasma free metanephrines.