The 24-hour urinary fractionated metanephrines:
normetanephrine (UNM) and metanephrine (NM) were measured by
HPLC–EC by using a commercial kit (Urinary metanephrines by HPLC,
BioRad, Milan, Italy) on an Agilent 1200 HPLC system (Agilent, Milan,
Italy) following the manufacturer's instructions.