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.
Norethisterone
Norethisterone was synthesized for the first time by chemists Luis Miramontes, Carl Djerassi, and George Rosenkranz at Syntex in Mexico City in 1951. It was derived from ethisterone, and was found to possess about 20-fold greater potency as a progestogen in comparison. Norethisterone was the first highly active oral progestogen to be synthesized, and was preceded (as a progestogen) by progesterone (1934), ethisterone (1938), 19-norprogesterone (1944), and 17α-methylprogesterone (1949) as well as by nandrolone (1950), whereas noretynodrel (1952) and norethandrolone (1953) followed the synthesis of norethisterone. The drug was first introduced, alone as "Norlutin", in the United States in 1957. Norethisterone was subsequently introduced in combination with mestranol as "Ortho-Novum" in the United States in 1963, and was the second progestin, after noretynodrel in 1960, to be used in an oral contraceptive. In 1964, additional contraceptive preparations containing norethisterone in combination with mestranol or EE, such as "Norlestrin" and "Norinyl", were marketed in the United States.