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.
Bioidentical hormone replacement therapy
Bioidentical hormones were first used for menopausal symptom relief in the 1930s, after Canadian researcher James Collip developed a method to extract an orally active estrogen from the urine of pregnant women and marketed it as the active agent in a product called Emmenin. It was supplanted on the market when its manufacturer, Ayerst (later Wyeth Pharmaceuticals), began producing the more easily manufactured conjugated equine estrogens in 1941 under the brand name Premarin; by 1992, Premarin was the most widely prescribed drug in the United States.