An<unk>  is a tumor of the pancreas that is derived from beta cells and secretes insulin. It is a rare form of a neuroendocrine tumor. Most<unk> s are benign in that they grow exclusively at their origin within the pancreas, but a minority metastasize.<unk> s are one of the functional pancreatic neuroendocrine tumor (PNET) group ("functional" because it increases production of insulin). In the Medical Subject Headings classification,<unk>  is the only subtype of "islet cell adenoma". Beta cells secrete insulin in response to increases in blood glucose. The resulting increase in insulin acts to lower blood glucose back to normal levels, at which point further secretion of insulin is stopped. In contrast, the secretion of insulin by<unk> s is not properly regulated by glucose, and the tumors continue to secrete insulin causing glucose levels to fall further than normal. As a result, patients present symptoms of low blood glucose (hypoglycemia), which are improved by eating. The diagnosis of an<unk>  is usually made biochemically with low blood glucose, elevated insulin, proinsulin, and C-peptide levels, and confirmed by localizing the tumor with medical imaging or angiography. The definitive treatment is surgery.
Insulinoma
Reactive hypoglycemia
Glucagonoma
Metastatic insulinoma
Somatostatinoma
Congenital hyperinsulinism
Idiopathic hypoglycemia
Adie syndrome