It was originally described simply as "brain hormone" by early workers such as Stefan Kopeć (1922)[1] and Vincent Wigglesworth (1934),[2] 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.
Thus, the brain was originally thought to be the source of the hormone that induces molting in insects.
[5][6] PTTH was first purified and identified from the silkworm Bombyx mori by Hiroshi Kataoka and colleagues with his menters Hironori Ishizaki and Akinori Suzuki in 1990.
[7] PTTH adopts the fold unique to the structural superfamily of the growth factors, such as NGF, TGF-β and PDGF.