Endocrine Abstracts

Background: Pheochromocytoma (PHEO) and paraganglioma (PGL) of abdominal origin secrete catecholamines which are metabolized to metanephrines. Head-and-neck paraganglioma (HNPGL) are considered as non secretary tumors.

Objectives: To find the utility of plasma free metanephrine (MN), normetanephrine (NMN) and 3-methxytyramine (3-MT) for the differential diagnosis PHEO/PGL after excluding MEN2 and VHL patients.

Methods: A total of 79 consecutive patients attending the AIIMS clinics based on clinical symptoms, histological findings and MRI reports were diagnosed with PHEO/PGL (benign (n=59), metastatic (n=9), MEN2 (n=7) and VHL (n=4)). 65 healthy age matched subjects were taken as controls. The subjects with MEN2 and VHL were excluded from the study. Plasma free metanephrines (MN, NMN and 3-MT) were estimated in 64 patients with PHEO/PGL by HPLC technique using ECD after solid phase extraction.

Results: The results of this study showed that plasma MN and NMN levels were high in 10 and 33% of patients with HNPGL where as in controls plasma MN and NMN were high in 3.9 and 1.5% respectively. The 3-MT was high in 53.3% of the patients as compare to controls (6.2%). In patients with PHEO/abdominal PGL, MN, NMN and 3-MT were high in 48, 96 and 53% respectively. The mean levels of MN, NMN and 3-MT were 167±260, 659±543 and 2.732±4.325 pg/ml respectively in HNPGL and 1.917±3.447, 7.150±11.454 and 4.752±7.329 pg/ml respectively in the patients with PHEO /abdominal PGL as compare to controls (110±195, 255±224 and 590±690) pg/ml respectively.

Conclusions: This study concludes that plasma NMN is useful biochemical marker for diagnosis of PHEO/ abdominal PGL after exclusion of patients with MEN2 and VHL, as compared to MN and 3-MT, with high sensitivity (96%) and specificity (98%). Plasma 3-MT can be useful in the identification of patients with HNPGL.