Endocrine pancreas

Topic Completed: 1 August 2012

Minor changes: 5 March 2020

Copyright: (c) 2002-2020,, Inc.

PubMed Search: Endocrine pancreas[TI] free full text[sb]

Deepali Jain, M.D.
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Cite this page: Jain D. Endocrine pancreas. website. Accessed August 3rd, 2020.
Definition / general
  • Consists of islets of Langerhans, represents 1% of pancreas (percentage higher at birth)
  • Round, compact, highly vascularized with scanty connective tissue
  • More irregular outline and trabecular arrangement in posterior head of pancreas with cells producing pancreatic polypeptide
  • Size of islets usually 0.1 to 0.2 mm, endodermal origin, one million islets present in pancreas
  • Islet composition: beta cells (68%), alpha cells (20%), delta cells (10%), PP cells (2%), serotonin cells (rare)
  • Postgastrectomy, may get islet hypertrophy, then beta cell proliferation, then atrophy and amylin deposits (Hum Pathol 2000;31:1368)
  • Alpha cells: produce glucagon; peripherally dense and round on EM
  • Beta cells: produce insulin and islet cell amyloid polypeptide (amylin), crystalline appearance on EM with surrounding halo
  • Delta cells: produce somatostatin (represses release of insulin and glucagon), large pale granules on EM
  • D1 cells: produce vasoactive intestinal polypeptide (VIP), which induces glycogenolysis and hyperglycemia, stimulates GI fluid secretion and causes secretory diarrhea
  • Enterochromaffin cells: synthesize serotonin, produce carcinoid syndrome
  • Gastrin cells: pancreas usually lacks gastrin producing cells, although gastrinomas are common
  • PP cells: produce pancreatic polypeptide, which stimulates secretion of gastric and intestinal enzymes and inhibits intestinal motility; present in islets and scattered in exocrine pancreas; more PP cells in posterior head of pancreas (from ventral bud)
  • Nesidioblastosis: islets in intimate association with ducts with formation of ductuloinsular complexes
  • Nesidiodysplasia: loss of the usual centrilobular concentration of larger islets, with increased small irregularly distributed aggregates of islet cells; also increase in beta cell nuclear size and DNA content; may be associated with endocrine neoplasms (Hum Pathol 1988;19:1215)
  • Peliosis: selective congestion and dilation of vessels of islets only, not seen in vessels elsewhere
Microscopic (histologic) images


Islets in newborn

Adult pancreas - ordinary type islet

Adult pancreas - irregular type islet

Adult pancreas: distribution of islet cell types

Islet rich in PP cells in posterior part of pancreatic head

Islets: cells with clear cytoplasm (centroacinar and ductal cells) stand out from a background of basophilic acinar cells

Nesidioblastosis in adult with persistent adult hyperinsulinemic hypoglycemia: clustering of irregular islets in vicinity of small ductules

Contributed by Dr. Cesare Bordi

Islet hyperplasia of Beckwith-Wiedemann syndrome: note crowding without fusion of islets inside pancreatic lobules

Images hosted on other servers:

Islets: cells with clear cytoplasm (centroacinar and ductal cells) stand out from a background of basophilic acinar cells

Electron microscopy images


Adult pancreatic islet cells

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Zymogen granules

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