Gastrin

In different. forms of oligopeptide (gastrointestinal neuropeptide hormone) of the stomach with 14, 17 or 34 amino acids. Gastrin is encoded by GAST, a gene located on chromosome 17: 37.12 - 37.13. Its production follows a circadian rhythm.

Gastrin is produced in the antrum of the stomach, there in the G-cells of the mucosa and reaches its target organs by haematogenesis. In the stomach mucosa, the peptide hormone binds to the gastrin receptors of the gastric cells (which are responsible for the formation and secretion of hydrochloric acid and the intrinsic factor). In addition, the main cells of the stomach mucosa are stimulated to form pepsinogen (the inactive precursor of pepsin) under the influence of gastrin.

Gastrin further enhances the cardiasphincter tone. Outside the stomach, gastrin stimulates the secretion of insulin, glucagon and somatostatin in the pancreas. The role of gastrin in oncogenesis is currently unclear.

Stimulation of gastrin formation through:

• stretching of the antrum by stomach contents (food),
• Exposure to protein degradation products (peptides),
• pH increase of the gastric juice >2.5
• Alcohol, nicotine and caffeine
• Inflammation of the antral gastric mucosa,
• GRP (gastrin-releasing peptides): is produced in the neuroendocrine cells of the stomach.

Inhibition of gastrin formation by:

• low pH of the stomach contents (pH<3)
• over-expansion of the stomach (autoregulation of acid secretion)
• Secretin (is formed in the duodenum)
• Somatostatin (is produced in the pancreas)
• GIP (gastrin inhibiting peptide) a glucose-dependent insulinotropic polypeptide
• GLP (glucacon-like peptide) released from L-cells of the ileum
• VIP (vasoactive intestinal peptide)
• Neurotensin

Standard value in serum: 90ng/l

Increased gastrin values are found:

• Bacterial gastritis
• Chronic atrophic gastritis, with/without pernicious anaemia (most common subtype of vitamin B12 deficiency anaemia)
• Gastrinom
• Hyperthyroidism (overactive thyroid)
• Short bowel syndrome - chronic digestive insufficiency that occurs after extensive resection of the small bowel - removal of small bowel parts
• Renal insufficiency
• Pyloric stenosis
• duodenal ulcer
• Drugs:
  • Antacids
  • H2-antagonists (e.g. Ranitidine)
  • Proton pump inhibitors (e.g. omeprazole)
• Gastrinoma (gastro-hepatic neuroendocrine tumor located in the pancreas, duodenum and antrum of the stomach).