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.
Nuggehalli Raghuveer Moudgal
Moudgal's early researches at the University of Madras were on the biochemistry of thyroid hormones but he shifted his focus to pituitary gonadotropins during his days at Choh Hao Li's laboratory at the University of California, Berkeley when he established that the hormones generated immune response in living beings and the discovery was reported to be a significant one as the belief till then was the principal function of the hormones was reproduction. Later, at Rodney Porter's laboratory in London, he worked on the role of cellulose as a carrier for immobilization of antibodies. Back in India, he expanded the scope of his researches to cover wider aspects of reproductive biology for which he established a Primate Research Laboratory at IISc in 1965, which was the largest primate house in the country at that time. Working on the macaques in his primate house, he discovered that sialidase from the kidney of the primate acted as an inhibitor of follicle stimulating hormone (FSH), a hormone responsible for pubertal development. He conducted elaborate studies on the molecular mechanism of Luteinizing Hormone (LH), a hormone which has significant role in ovulation and testosterone production, and elucidated the "unfolding of LH binding to LH receptors in the target cell" which was detailed in one of his articles, "Effect of ICSH on Early Pregnancy in Hypophysectomized Pregnant Rats", published in Nature in 1969. He discovered that neutralizing LH resulted in neutralization of several reproductive functions such as ovulation, implantation, and gestational progress and the discovery opened a new methodology in immunocontraceptive technology. Later, he furthered his investigations on hormone actions by using antibodies as probes. His findings reportedly prompted R. O. Greep of Harvard University to invite him for collaborative research and Moudgal supervised the work of Greep's Group at his laboratory. At Harvard, he also collaborated with W. R. Moyle and established the presence of Luteinizing hormone/choriogonadotropin receptors on tumor cells in the testicles for the first time, which they revealed in an article, "Specific binding of luteinizing hormone to Leydig tumor cells", published in the Journal of Biological Chemistry in 1971. He used these tumor cells for further investigations on Hormone-Receptor interactions, Cyclic adenosine monophosphate (cyclic AMP) production and steroidogenesis and experimentally demonstrated the extent of coupling and response with regard to cyclic AMP production and steroid output.