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.
Prasterone
DHEA was discovered, via isolation from male urine, by Adolf Butenandt and in 1934, and the compound was isolated from human blood plasma by Migeon and Plager in 1954. DHEA sulfate, the 3β-sulfate ester of DHEA, was isolated from urine in 1944, and was found by Baulieu to be the most abundant steroid hormone in human plasma in 1954. From its discovery in 1934 until 1959, DHEA was referred to by a number of different names in the literature, including "dehydroandrosterone", "transdehydroandrosterone", "dehydroisoandrosterone", and "androstenolone". The name "dehydroepiandrosterone", also known as "DHEA", was first proposed by Fieser in 1949, and subsequently became the most commonly used name of the hormone. For decades after its discovery, DHEA was considered to be an inactive compound that served mainly as an intermediate in the production of androgens and estrogens from cholesterol. In 1965, an association between DHEA sulfate levels and aging was reported by De Nee and Vermeulen. Following this, DHEA became of interest to the scientific community, and numerous studies assessing the relationship between DHEA and DHEA sulfate levels and aging were conducted.