The PP cell accounts for about one percent of islet cells and secretes the pancreatic polypeptide hormone.An inhibiting hormone, pancreatic somatostatin inhibits the release of both glucagon and insulin. Recall that somatostatin is also released by the hypothalamus (as GHIH), and the stomach and intestines also secrete it. The delta cell accounts for four percent of the islet cells and secretes the peptide hormone somatostatin.Elevated blood glucose levels stimulate the release of insulin. The beta cell produces the hormone insulin and makes up approximately 75 percent of each islet.Glucagon plays an important role in blood glucose regulation low blood glucose levels stimulate its release. The alpha cell produces the hormone glucagon and makes up approximately 20 percent of each islet.The pancreatic islets each contain four varieties of cells: Cells and Secretions of the Pancreatic Islets View the University of Michigan WebScope to explore the tissue sample in greater detail.