Prothoracicotropic hormone
Prothoracicotropic hormone (PTTH) was the first insect hormone to be discovered. It was originally described simply as "brain hormone" by early workers such as Stefan Kopeć (1922) and Vincent Wigglesworth (1934), who realized that ligation of the head of immature insects could prevent molting or pupation of the body region excluded from the head if the ligation was performed before a critical age in the lifestage was reached. After a certain point the ligation had no effect and both sections of the insect would molt or pupate. However, implantation of a conspecific brain to a sessile ligated abdomen or an abdomen under diapause would induce molting or pupation. Thus, the brain was originally thought to be the source of the hormone that induces molting in insects.
Christian de Duve
Sutherland had been working on the insulin-impurity substance and had named it hyperglycemic-glycogenolytic (HG) factor. He and de Duve immediately discovered that the HG factor was synthesised not only by the pancreas but, surprisingly, by the gastric mucosa and certain other parts of the digestive tract. They further found that the hormone was produced from pancreatic islets by cells differing from the insulin-producing beta cells, presumably the alpha cells. It was de Duve who realised that Sutherland's HG factor was glucagon, and this rediscovery led to its permanent name, which he reintroduced it in 1951. They showed that glucagon was the major hormone influencing the breakdown of glycogen (glycogenolysis) in the liver, by which more sugars are produced in the blood.