Oxytocin was the first hormone to have its structure identified and to be synthesized in the laboratory. This was achieved in 1953 by two groups, one working in France and the other in the United States. The hormone plays an important role in birth and in feeding the infant. It has two major actions, the first being to promote contractions of the uterus, an action which is used in obstetric practice when the hormone is infused if labour is protracted. The second action is to cause contraction of the muscular elements surrounding the alveoli and milk ducts in the breasts, thereby helping to expel the milk (milk let-down). Oxytocin is ... found in men, but its role is not clear, although it has been suggested that it aids sperm transport during mating.