Secretin

n. hormone produced in the small intestine which stimulates the secretion of bile and pancreatic juices (Biochemistry)

Secretin is a peptide hormone produced in the S cells of the duodenum in the crypts of Lieberkühn. Its primary effect is to regulate the pH of the duodenal contents via the control of gastric acid secretion and buffering with bicarbonate. It was the first hormone to be discovered.
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Secretin /se·cre·tin/ a hormone secreted by the duodenal and jejunal mucosa when acid chyme enters the intestine; it stimulates secretion of [more]Secretin - Community and Resources

Noun
1. peptic hormone produced by the mucous lining of the small intestine; can stimulate secretion by the pancreas and liver
(hypernym) hormone, endocrine, internal secretion

Hormone made by glands in the small intestine that stimulates pancreatic secretion. The word "hormone" was coined by the English physiologists Wm. M. Bayliss and Ernest H. Starling in connection with their discovery of secretin, the first hormone, in 1902.