The sympathoadrenal system has been shown to stimulate the secretory activity of enteroendocrine cells, although the response is transient. Our aim was to investigate the effects of long-term catecholamine excess on circulating glucagon-likepeptide-1 (GLP-1) levels in patients with pheochromocytoma/paraganglioma (PPGL). Thirty patients diagnosed with PPGL were analyzed. A significant negative association was observed between fasting plasma GLP-1 levels and elevated plasma-free metanephrine ( r = − 0.407 , p = 0.026 ). After adjustment for age, sex, body mass index (BMI), serum creatinine, and the presence of hyperglycemia, the negative association between plasma GLP-1 and metanephrine persisted by multiple linear regression analysis ( β = − 0.493 , p = 0.013 ). Positive correlations between fasting glucose and plasma metanephrine ( r = 0.380 , p = 0.038 ) and normetanephrine levels ( r = 0.450 , p = 0.013 ) were also found. Mean fasting levels of total GLP-1 increased significantly from 25.81 to 39.01 pmol/L ( p = 0.017 ) after PPGL resection. In conclusion, long-term overproduction of catecholamines appears to induce suppression of GLP-1 production compared to an acute response to a stress stimulus. Further studies are required to elucidate the mechanism of GLP-1 secretion with chronic exposure to catecholamine.