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.
Christine Jorgensen
Jorgensen was faced with a world that placed strong societal emphasis on adhering to gender binaries and strict notions of masculinity and femininity. When Jorgensen was first exposed to the book "The Male Hormone" in the 1940s, the same traditional ideas of masculinity were reinforced through its pages. As the book posed, masculinity could be restored to individuals by utilizing male hormones. It was then that Jorgensen realized that the attitudes of the book were not aligned with her personal experiences and questions about gender identity. She refused to dismiss her personal sentiments and questions as confusion about sexuality and began taking estrogen. The significance of Jorgensen choosing this path was one of the first stages of transgender identity being legitimized and explored as a subject for both Jorgensen and the American public. Jorgensen's highly publicized transition helped bring to light gender identity and shaped a new culture of more inclusive ideas and accepting notions about the subject.