Oxytocin

A hormone made in the brain that plays a role in childbirth and lactation by causing muscles to contract in the uterus (womb) and the mammary glands in the breast. Animal studies have shown that oxytocin also has a role in pair bonding, mate-guarding, and social memory. Oxytocin is a peptide (a compound consisting of 2 or more amino acids) that is secreted by the hypothalamus and transported to the posterior lobe of the pituitary gland at the base of the brain. Oxytocin is related to another hormone called vasopressin.

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A nonapeptide neurohypophysial hormone, differing from human vasopressin in having leucine at position 8 and isoleucine at position 3, that causes myometrial contractions at term and promotes milk release during lactation; used for the induction or stimulation of labor, in the management of postpartum hemorrhage and atony, and to relieve painful breast engorgement. SYN: ocytocin. [G. okytokos, swift birth]

- arginine o. o. with arginine at position 8 (identical to arginine vasotocin). SEE ALSO: arginine vasopressin.

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oxy·to·cin -'tōs-ən n

1) an octapeptide hormone C₄₃H₆₆N₁₂O₁₂S₂ secreted by the anterior lobe of the pituitary gland that stimulates esp. the contraction of uterine muscle and the secretion of milk called also alpha-hypophamine

2) a synthetic version of oxytocin used esp. to initiate or increase uterine contractions (as in the induction of labor) see PITOCIN

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n.

a hormone, released by the pituitary gland, that causes contraction of the uterus during labour and stimulates milk flow from the breasts by causing contraction of muscle fibres in the milk ducts. Intravenous infusions of oxytocin (Syntocinon) are used to induce uterine contractions and to control or prevent postpartum haemorrhage.

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oxy·to·cin (ok″se-toґsin) a nonapeptide secreted by the magnocellular neurons of the hypothalamus and stored as a posterior pituitary hormone along with vasopressin. It promotes uterine contractions and milk ejection and contributes to the second stage of labor. [USP] a preparation of this substance obtained from the neurohypophyses of domestic food animals or produced synthetically; it is administered intramuscularly or intravenously to induce labor, increase the force of uterine contractions, contract uterine muscle after delivery of the placenta, and control postpartum hemorrhage, and intranasally to stimulate milk ejection. In veterinary medicine it is used to stimulate letdown of milk in cows with agalactia.