Secretin
Hormone that neutralizes duodenal pH and regulates water balance.
Last updated
Secretin is a peptide hormone produced in the S cells of the duodenum that regulates water homeostasis, influences duodenal pH, and modulates secretions in the stomach, pancreas, and liver. Secretin is encoded by the SCT gene in humans and plays roles in digestion, osmoregulation, and food intake.
Quick Facts
- Discovered by
- William Bayliss and Ernest Starling
- Type
- Peptide hormone
- Gene
- SCT
- Primary function
- Regulates duodenal pH and water homeostasis
- Amino acids
- 27
Facts from the source article.
Lore & Background
They discovered that cutting all nerves to the pancreas did not prevent pancreatic secretion in response to chyme entering the duodenum, indicating a chemical messenger transported via blood. The mature peptide is 27 amino acids long with a helix between positions 5 and 13. It shares sequence similarities with glucagon, vasoactive intestinal peptide (VIP), and gastric inhibitory peptide (GIP).
Secretin release is triggered by low duodenal pH (2–4.5) and inhibited by H2 antagonists that reduce gastric acid. Secretin neutralizes duodenal pH by stimulating bicarbonate secretion from pancreatic ductal cells and cholangiocytes, inhibiting gastric acid secretion, and promoting water and bicarbonate from Brunner's glands. Secretin reduces food intake via the central melanocortin system and is used in diagnostic tests for pancreatic function.
Reader's Guide
Although adrenaline was identified earlier, secretin's discovery catalyzed the field of hormonal regulation. Its primary physiological role—neutralizing duodenal pH to enable optimal pancreatic enzyme function—is critical for digestion.
Beyond digestion, secretin's roles in osmoregulation and food intake reveal its broader influence on homeostasis. A wave of interest in secretin as a treatment for autism in the 1990s was disproven by NIH clinical trials. Secretin remains a model for understanding hormone action, receptor signaling, and the integration of digestive and fluid balance systems.
Did You Know?
- Secretin is canonically recognized as the first hormone—the term 'hormone' was coined based on its discovery.
Frequently Asked Questions
Who is Secretin?
Secretin is a 27-amino-acid peptide hormone made by the S cells of the duodenal wall and encoded by the SCT gene in humans. It holds the distinction of being the first hormone ever identified, marking the birth of endocrinology.
What is Secretin known for?
Its core job is to raise duodenal pH by prompting the pancreas and liver to release bicarbonate-rich fluid that neutralizes incoming acidic chyme. It also fine-tunes water homeostasis and dampens gastric acid secretion.
Who discovered Secretin?
William Bayliss and Ernest Starling isolated its action in 1902 and coined the name 'secretin' because it caused the pancreas to secrete its digestive juice. Their experiment is widely regarded as the founding moment of the hormone concept.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Secretin (CC BY-SA 4.0).
- Word definitions: the Codexery glossary, each quoted from its Wikipedia article.
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