Secretin
Secretin was the first hormone to be identified. In 1902, William Bayliss and Ernest Starling were studying how the nervous system controls the process of digestion. It was known that the pancreas secreted digestive juices in response to the passage of food (chyme) through the pyloric sphincter into the duodenum. They discovered (by cutting all the nerves to the pancreas in their experimental animals) that this process was not, in fact, governed by the nervous system. They determined that a substance secreted by the intestinal lining stimulates the pancreas after being transported via the bloodstream. They named this intestinal secretion "secretin". Secretin was the first such "chemical messenger" identified. This type of substance is now called a hormone, a term coined by Bayliss in 1905.
Percy Lavon Julian
Julian's research at Glidden changed direction in 1940 when he began work on synthesizing progesterone, estrogen, and testosterone from the plant sterols stigmasterol and sitosterol, isolated from soybean oil by a foam technique he invented and patented. At that time clinicians were discovering many uses for the newly discovered hormones. However, only minute quantities could be extracted from hundreds of pounds of the spinal cords of animals.