Plasma and Urine Total Antioxidant Capacity in Patients With Adrenal Tumors

Total antioxidant capacity better characterizes the redox status of the biological system than the determination of individual antioxidants separately. This study is the first to assess the total antioxidant/oxidant status in the plasma and urine of patients with adrenal tumors. The study group consisted of 60 patients (31 women and 29 men) with adrenal masses, classified into three subgroups: non-functional incidentaloma, pheochromocytoma and Cushing’s/Conn’s adenoma. The number of patients was set a priori based on our previous experiment (α = 0.05, test power = 0.9) Plasma total antioxidant capacity (TAC) was increased in incidentaloma patients, whereas in pheochromocytoma group was decreased. Plasma and urine total oxidant status (TOS) and oxidative stress index (OSI) were significantly higher in patients with adrenal tumors. Ferric reducing antioxidant potential (FRAP) was decreased in plasma and urine, while DPPH (2,2-diphenyl-1-picrylhydrazyl) antiradical activity only in plasma of patients with adrenal masses. In pheochromocytoma patients, plasma and urine TAC, as well as plasma DPPH and FRAP correlated positively with methanephrine and normethanephrine. Reduced levels of TAC, DPPH and FRAP clearly indicate a reduced ability to scavenge free radicals and thus a lack of effective protection against oxidative stress in patients with adrenal tumors. Therefore, those patients are especially vulnerable to oxidative stress and oxidative damage, which can lead to impaired cellular metabolism. Both plasma and urine redox biomarkers can be used to assess systemic antioxidant status in adrenal tumor patients.