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.
Bertold Wiesner
During 1926 while Wiesner was still in Austria, he began investigating the role of hormones in regulating fertility and their impact on fetal development. Wiesner also researched the possibility of preventing and terminating pregnancy by physiological means without mechanical intervention based on oral ingestion of manufactured substances containing hormones. He presented his first paper at the First International Congress for Sex Research organized by the psychiatrist Albert Moll in Berlin.