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The endocrine (hormone-releasing) cells that regulate blood sugar levels and appetite are located in a group of patchy and irregular shaped areas in the pancreas known as the Islets of Langerhans. Nearly one million Islets are evenly distributed around the pancreas. Each of these individual cells in the Islets contains specific hormones that signal the body that it has too much glucose or not enough. Glucose (sugar) is required by the body for energy. Too much or too little glucose in the body can have a negative effect. The hormone producing cells in the Islets are:

• Alpha cells – produce hormones glucagon and ghrelin
• Beta cells – produce hormones insulin and amylin
• Delta cells - produce hormone somatostatin
• Epsilon cells - produce hormone ghrelin
• Gamma (F-cells or PP-cells) cells – produce polypeptide hormone

Alpha cells in the islets of Langerhans produce the hormone glucagon and ghrelin. Glucagon is released when glucose levels in the blood are low and glucagon stimulates the liver to convert glycogen to glucose. The ghrelin hormone signals the hypothalamus in the brain to stimulate the feeling of appetite. Body temperature, hunger, thirst, fatigue, anger, and sleep are controlled by the hypothalamus. An increase of ghrelin hormones are found before meals and are decreased after meals.

Beta cells produce the hormones insulin and amylin. Beta cells make up about 70 percent of the Islets. Insulin is manufactured, stored, and secreted by the beta cells. Glucose moves from the blood into the body’s cells by the hormone insulin. Insulin assists in the metabolism of the glucose. Amylin is very similar to insulin in that it helps to reduce glucose in the blood. Amylin decreases the secretion of glucagon and moderates the emptying of the stomach,

Delta cells in the islets produce the hormone somatostatin. The endocrine system is regulated by the peptide hormone somatostatin. Pancreatic somatostatin inhibits the release of glucagon and insulin.

Epsilon cells (ε-cells) are a newer found cell type in the Islets that appear to only produce the hormone ghrelin.

Gamma cells (also known as F Cells or PP cells) are pancreatic polypeptide (PP) producing cells. The PP cells are mainly found in the Islets of Langerhans at the head of the pancreas. The pancreatic polypeptide hormone is expressed at times when glucose levels in the blood are low. This can be created from fasting, exercising, eating protein meals, or from being hypoglycemic (low blood sugar). The increase of somatostatin and glucose in the blood decrease the polypeptide hormone levels. Having too little PP hormones appears to stimulate appetite, lessens the ability to resist the temptation of food, and increases the chances of a person becoming overweight.

During embryonic pancreatic and islets development, expression of Neurogenin-3 is critical to the functioning of the hormonal cell types found in the islets. Scientist at the University Louis Pasteur (ULP) in France, have identified that neurogenin-3 does not effect the production of insulin or glucagon, but instead signals precursors Pdx1, Isl1, Pax4, Pax6, NeuroD, Nkx2.2, and Hlxb9 that regulate the development of islet cells at different stages. In inactive nuerogenin-3 mice Isl1, Pax4, Pax6, and NeuroD are not expressed and the four endocrine cell-types fail to generate in the islets causing diabetes resulting in postnatal death.