FGF-21 LEVELS ARE ELEVATED IN PHEOCHROMOCYTOMA AND DIMINISH AFTER TUMOR REMOVAL RELATIVE TO GLUCOSE NORMALISATION

Objective: Fibroblast Growth Factor 21 (FGF-21) is a novel hepatokine with many beneficial effects on metabolism. The aim was to evaluate the relationship between plasma FGF-21, energy, lipid and glucose metabolism in patients with pheochromocytoma/functional paraganglioma (PPGL) in comparison with obese patients and lean healthy controls. Design and method: We examined 40 consecutive patients with PPGL, 21 obese and 26 lean healthy controls. 27 patients with PPGL were examined one year after adrenalectomy. Basic anthropometric and biochemical measurements were done. Energy metabolism was measured by indirect calorimetry (Vmax-Encore 29N). FGF-21 was measured by ELISA. Results: FGF-21 was significantly higher in PPGL than in controls (174.2 [283] pg/ml vs. 107.9 [116] pg/ml; P < 0.001) and comparable with obese (174.2 [283] pg/ml vs. 160.4 [180]; P = NS). After adrenalectomy FGF-21 decreased (176.4 [284] pg/ml vs. 131.3 [225] pg/ml, p < 0.001). Higher levels of FGF-21 have been expressed particularly in patients with diabetes. FGF-21 positively correlated in PPGL with age (p = 0.005), BMI (p = 0.028), fasting blood glucose (p = 0.002) and glycated hemoglobin (p = 0.014). Patients with pheochromocytoma showed hypermetabolic status compared to other groups. We did not find the relationship between indirect calorimetry parameters and FGF-21. Conclusions: Long-term catecholamine overproduction in PPGL leads to elevation in plasma FGF-21, especially in patients with secondary diabetes. FGF-21 levels were comparable between obese and PPGL patients despite different anthropometric indices. We didn’t find a link between FGF-21 and hypermetabolism in PPGL. It seems that hyperglycemia is basic stimulus for secretion of circulating FGF-21 regardless of etiology.