Interpreting Normetanephrines-the Significance of Clinical Context

Abstract

Introduction: Pheochromocytoma ranges in presentation, but the diagnostic hallmarks are increased catecholamine secretion in patients with an adrenal mass. However, interpretation requires consideration of the clinical state. Case: A 60-year-old man presented with 6 months of episodic flushing, night sweats, fatigue, back pain, and 20-pound weight loss. Vitals were notable for hypotension and mild tachycardia. He was thin with evidence of hyperpigmentation. Contrasted CT showed 15 cm heterogeneous masses of both adrenals and a rib lesion. Plasma normetanephrines were elevated on two separate measures (526 and 1,398 pg/mL, nl <=148). Plasma metanephrines were normal. Urine normetanephrines were increased 4-fold (2,165mcg/g Cr, n 108–524). Labs noted low DHEA-S (2 mcg/dL, n 38–313), high ACTH (204 pg/mL, n 6–50), random cortisol (5.2 mcg/dL, n 3.5–18.3), undetectable aldosterone, and high plasma renin activity (83 ng/mL/h, n 2.9–10.8). Cortisol peaked at 6.7 mcg/dL 1 hour after 250mcg of cosyntropin. MRI revealed over 15cm infiltrating masses arising from adrenals with modest flare on T2 imaging. Dotatate PET/CT showed mild uptake of bilateral adrenals and metastases to liver and bone. He was started on steroid replacement and doxazosin for presumed pheochromocytoma.He was transferred to our facility where he remained hypotensive despite adequate glucocorticoid and mineralocorticoid replacement. Once stabilized, repeat plasma normetanephrines were insignificant (218 pg/mL, n 0–145) and chromogranin was normal (68 ng/mL, n<93). Biopsy of the rib lesion confirmed diffuse large B-cell lymphoma. Discussion: Pheochromocytoma classically presents in the outpatient setting with palpitations, diaphoresis, pallor, and paroxysmal hypertension. Rarely, it results in hypertensive emergencies requiring hospitalization. In patients with catecholamine excess and an adrenal mass, pheochromocytoma is usually suspected. 3-fold or more increases of normetanephrines or metanephrines above upper cutoffs are rarely false-positives. However, this assumes clinical stability. Sympathoadrenal activation is a physiologic response to acute illness. Metanephrines in critically ill patients without pheochromocytoma approached those of pheochromocytoma in one study. Levels normalized upon recovery from illness, highlighting the importance of verifying biochemistries once the patient is stable. The degree of elevation in normetanephrines seen in this patient was a physiologic response to adrenal insufficiency and clinical instability. Pathology confirmed lymphoma rather than pheochromocytoma for which he was started on chemotherapy. Conclusion: Elevated normetanephrines is an appropriate physiological response in the acutely ill. Careful consideration of the clinical picture in conjunction with biochemical data is critical.