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.
Estradiol benzoate
Estradiol benzoate was one of the first estrogens to be developed and marketed. In 1931, Adolf Butenandt found that the benzoic acid ester of estrone had a prolonged duration of action. Schwenk and Hildebrant discovered estradiol via reduction of estrone in 1933, and they proceeded to synthesize estradiol benzoate from estradiol the same year. Estradiol benzoate was patented by Schering in 1933, and then by Schering-Kahlbaum in 1936 in an oil preparation for injectable use, and was introduced later that year in 1936 under the brand name Progynon-B. Following its introduction, estradiol benzoate, along with estradiol dipropionate, were the most widely used esters of estradiol for many years. However, estradiol valerate and estradiol cypionate, which are longer-acting esters that require less frequent administration, were developed and introduced in the 1950s, and have since largely superseded estradiol benzoate and estradiol dipropionate.