Chromogranin A is a secretory protein. It is located in the large, dense-core vesicles of neuroendocrine cells. Chromogranin A-derived peptides are involved in a range of activities, like glucose metabolism, tumour angiogenesis, regulation of blood pressure and neuroprotection. Neuroendocrine cells have nerve and hormone aspects and are found in all organs of the body. These cells can give rise to both benign and malignant tumours. Many of these tumours release large quantities of hormones like catecholamines, insulin or serotonin. Some of the tumours do not release these hormones. However, all neuroendocrine tumours are often associated with inflated concentrations of Chromogranin A.