Endocrine Abstracts

Introduction: Pheochromocytomas (PHEOs) are tumors arising from medulla chromaffin cells. Their diagnosis is challenging due to a large clinical spectrum – from classical crisis to completely asymptomatic. Approximately 5.0–6.5% of adrenal incidentalomas are pheochromocytomas, and 8% of pheochromocytomas are completely asymptomatic, usually in a familial form.

Aim: To compare biochemical and imagistic features of symptomatic/asymptomatic PHEOs.

Methods: A retrospective study including 47 patients diagnosed with PHEO between 2012-2018, divided in two groups. Group 1: 6 with asymptomatic PHEO (3F, 3M, aged 53.8±19.2 years) had MEN 2A, without any history of signs suggestive of PHEO crisis, discovered with the occasion of routine MEN2A follow-up. Group 2: 41 patients with typical manifestations of PHEO (31F, 10M, aged 56.6±16 years, 2 with MEN 2A). We compared plasma free metanephrines & normetanephrines levels and tumor size (CT scan) in patients with asymptomatic PHEO with those in patients with symptomatic PHEO. The data were shown as mean ±s.d.

Results: Plasma free metanephrines (normal 10–90 pg/ml) in asymptomatic PHEOs patients were 193±201.7 pg/ml, compared to 93.8±87.9 pg/ml, in patients with symptomatic PHEO. Plasma free normetanephrines (normal 20-200 pg/ml) in asymptomatic patients were 1247±1290 pg/ml compared to 414.35±709.7 pg/ml, in symptomatic patients. Although the values seemed paradoxically higher in asymptomatic patients, there were no significant differences between the 2 groups. Predominant secretion of metanephrines was observed in 66.6% of patients from group 1, as compared with 15% in group 2. Tumors were situated predominantly in the right adrenal in both groups (in 4/6 patients in group 1 and in 24/41 patients, in group 2). Bilateral tumors were noted in one symptomatic patient. The maximal tumor diameter in group 1 was 38.3±19.2 mm, while in group 2 was 52.4±25 mm, (P=0.005). Correlating tumor size with metanephrines levels, there is a statistically valid association in both groups (P<0.001).

Conclusion: Patients with asymptomatic PHEO had smaller tumors, but similar plasma metanephrines levels compared with patients with symptomatic PHEO. It is tempting to speculate that the poor response of peripheral tissues to catecholamine hypersecretion in patients with asymptomatic PHEOs may be due to chronic receptor down-regulation and relatively stable catecholamine tumor secretion in time.