Secretin is a hormone of the gastrointestinal tract. It is secreted by the duodenal wall of the small intestine when hydrochloric acid passes from the stomach into the duodenum, secretin is released into the bloodstream. This hormone stimulates pancreas for synthesis and secretion of non enzymatic part of pancreatic juice. It also stimulates liver for secretion of bile juice and inhibit the gastric acid secretion in stomach and reduce rate of contraction of stomach.