Unilateral and Bilateral Adrenalectomy for Pheochromocytoma Requires Adjustment of Urinary and Plasma Metanephrine Reference Ranges

Abstract

Follow-up after adrenalectomy for pheochromocytoma is recommended because of a recurrence risk. During follow-up, plasma and/or urinary metanephrine (MN) and normetanephrine (NMN) are interpreted using reference ranges obtained in healthy subjects. Because adrenalectomy may decrease epinephrine production, we compared MN and NMN concentrations in patients after adrenalectomy to concentrations in a healthy reference population. A single-center cohort study was performed in pheochromocytoma patients after adrenalectomy between 1980 and 2011. Seventy patients after unilateral and 24 after bilateral adrenalectomy were included. Plasma-free and urinary-deconjugated MN and NMN determined at 3 to 6 months and annually until 5 years after adrenalectomy were compared with concentrations in a reference population. Data are presented in median (interquartile range). Urinary and plasma MN concentrations 3 to 6 months after unilateral adrenalectomy were lower compared with the reference population (39 [31-53] μmol/mol creatinine and 0.14 [0.09-0.18] nmol/L vs 61 [49-74] μmol/mol creatinine and 0.18 [0.13-0.23] nmol/L, respectively, both P < .05). Urinary MN after bilateral adrenalectomy was reduced even further (7 [1-22] μmol/mol creatinine; P < .05). Urinary and plasma NMN were higher after unilateral adrenalectomy (151 [117-189] μmol/mol creatinine and 0.78 [0.59-1.00] nmol/L vs 114 [98-176] μmol/mol creatinine and 0.53 [0.41-0.70] nmol/L; both P < .05). Urinary NMN after bilateral adrenalectomy was higher (177 [106-238] μmol/mol creatinine; P < .05). Changes in urinary and plasma MNs persisted during follow-up. Concentrations of MN are decreased, whereas NMN concentrations are increased after unilateral and bilateral adrenalectomy. Adjusted reference values for MN and NMN are needed in the postsurgical follow-up of pheochromocytoma patients.