This is an image of a normal islet of Langerhans. These islets are scattered throughout the entire pancreas and form the endocrine pancreas. They are composed of different cell types, which can be differentiated by the hormone they produce:

• beta cell produces insulin (hypoglycemia);

• alpha cell produces glucagon (hyperglicemia);

• delta cell produces somatostatin (suppresses both insulin and glucagon secretion);

• PP cell produces pancreatic polypeptide (PP) (gastrointestinal effects);

• D1 cell produces vasoactive intestinal polypeptide (VIP) (hyperglycemia, secretory diarrhea);

• enterochromaffin cell produces serotonin.

The main disorders of islet cells are: 1) diabetes mellitus and 2) pancreatic endocrine tumors. Type 1 diabetes is characterized by insulitis, which represents lymphocytic (T cell lymphocytes) infiltrate of the islets. Type 2 diabetes is characterized by amyloid deposition within the islets.