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.
Prasterone
DHEA was discovered, via isolation from male urine, by Adolf Butenandt and in 1934, and the compound was isolated from human blood plasma by Migeon and Plager in 1954. DHEA sulfate, the 3β-sulfate ester of DHEA, was isolated from urine in 1944, and was found by Baulieu to be the most abundant steroid hormone in human plasma in 1954. From its discovery in 1934 until 1959, DHEA was referred to by a number of different names in the literature, including "dehydroandrosterone", "transdehydroandrosterone", "dehydroisoandrosterone", and "androstenolone". The name "dehydroepiandrosterone", also known as "DHEA", was first proposed by Fieser in 1949, and subsequently became the most commonly used name of the hormone. For decades after its discovery, DHEA was considered to be an inactive compound that served mainly as an intermediate in the production of androgens and estrogens from cholesterol. In 1965, an association between DHEA sulfate levels and aging was reported by De Nee and Vermeulen. Following this, DHEA became of interest to the scientific community, and numerous studies assessing the relationship between DHEA and DHEA sulfate levels and aging were conducted.