A high rate of modestly elevated plasma normetanephrine in a population referred for suspected PPGL when measured in a seated position.

Objective: Determine rate of high plasma normetanephrine or metanephrine (PNM-PMN) in a large sample of patients according to PNM-PMN posture and age-adjusted references.

Design: Retrospective re-analysis of PNM-PMN from a Canadian reference laboratory (n = 5452), 2011-2015; most were in seated position (n = 5112) rather than supine (n = 340). An international PPGL database demonstrated expected distribution of supine PNM-PMN in PPGL patients.