When the pH of the chyme entering the duodenum drops to 2.0 or below, the inhibitory influence of the intestinal phase is greatest. Acidic chyme in the duodenum inhibits CNS stimulation and initiates local reflexes that inhibit gastric secretion. Acidic chyme also stimulates the duodenum to release the hormone secretin, which enters the blood and is carried to the stomach, where is inhibits gastric secretion. Fatty acids and certain other lipids in the duodenum initiate the release of the hormone cholecystokinin, which also inhibits gastric secretion.