Discovery of eCG

eCG is discovered by Harold Cole and George Hart when they realize that injecting serum from pregnant mares into immature rats induced their sexual maturity. The bioactive component in serum mediating these effects is termed pregnant mare serum gonadotropin, or PMSG.

Harold Cole and R. F. Miller show that PMSG can induce ovulation and oestrum in ewes during the anoestrous period, i.e. outside the breeding season, showing its potential for use in farming.

An international standard for PMSG is established. Shortly afterwards the sale of pharmaceutical preparations of PMSG commences. It is originally marketed for women but is later discontinued for that purpose. It however continues to be sold for animals, initially mainly for research, but increasingly for practical uses as evidence of efficacy from research accumulates.

Cole and Harold Goss find out that PMSG is produced and secreted by the endometrial cups, ulcer-like protuberances surrounding the foetus at the surface of the endometrium early in pregnancy. Their origins are unclear but are thought to be maternal.

Robert Moor and W.R. Allen realize that the endometrial cups are in fact of embryonic origin as the chorionic girdle is their progenitor. The chorionic girdle is a thick band of trophoblast which surrounds the conceptus between days 25 and 35 in pregnancy. This leads to PMSG being renamed with its current nomenclature, to equine chorionic gonadotropin, or eCG.

Production of eCG in Iceland starts.

eCG is an important component in veterinary drugs, used worldwide for induction and synchronization of ovulation in animals, both farmed and wild.