Thus, the co-occurrence of pheochromocytoma in individuals with NF1 might have a combined effect on glucose metabolism and insulin homeostasis, resulting in clinical hypoglycemia. Notably, hypoglycemia in pheochromocytoma is often observed postoperatively; however, there are rare reports of preoperative hypoglycemia due to alternative mechanisms. This evidence concerns the gene INS and hereditary pheochromocytoma-paraganglioma.