
n.
A short polypeptide hormone, C43H66N12O12S2, released from the posterior lobe of the pituitary gland, that stimulates the contraction of smooth muscle of the uterus during labor and facilitates ejection of milk from the breast during nursing.
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American Heritage Dictionary:
ox·y·to·cin |

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Word Overheard by Answers.com:
oxytocin |
New York Times columnist David Brooks turned his attention to the hormone oxytocin, which aids in forming and maintaining relationships. He named this ability as the best predictor of success for both individuals and organizations:
"Oxytocin is a hormone that helps mammals bond.... In humans, oxytocin levels rise during childbirth, breast feeding and sex. Humans with higher oxytocin levels are more likely to trust other people.... I figure if we can hang Oxytocin Meters around people's necks, we can tell who is involved in healthy relationships and who isn't."
Link: Of Human Bonding
Posted July 3, 2006.
See our Word Overheard blog to see interesting uses of strange words.
Oxford Companion to the Body:
oxytocin |
Oxytocin is one of the two major hormones secreted from the posterior lobe of the pituitary gland, the other being vasopressin, the antidiuretic hormone. The posterior pituitary itself largely comprises endings of nerves whose cell bodies lie in the brain in the hypothalamus. Its hormones are extruded from the nerve endings directly into blood capillaries and thence into the general circulation. Oxytocin is a relatively small peptide hormone, composed of only 9 amino acids. It is synthesized in nerve cells in the hypothalamus in the form of a larger, precursor molecule, which is transported down the nerve fibres through the pituitary stalk to the posterior lobe. The active hormone is cleaved from the precursor during this process.
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 also found in men, but its role is not clear, although it has been suggested that it aids sperm transport during mating. The stimuli for release reflect the actions of the hormone and its actions are rapid because they are evoked by sensory nerve impulses which communicate with the hypothalamic nerve cells. Thus it is released during vaginal stimulation, so that during the process of birth, as the infant enters the birth canal, oxytocin is released and in turn causes increased uterine activity, allowing the process to proceed more rapidly. The oxytocin released at this time may also cause milk ejection, a response known as Ferguson's reflex. This reflex was first described in 1942, although herdsmen had been aware of it for centuries and had used it as an aid to milking; in the second century ad, Galen, the Greek physician and prolific writer, described how herdsmen would blow into the vagina of mares to improve milk yield. Oxytocin is also released in response to suckling and many other stimuli associated with breast feeding, such as the sight and sound of the infant. If the mother is not relaxed, this may act via the hypothalamus to inhibit oxytocin release so that problems with breast feeding may arise.
Interestingly, there have been no descriptions of clinical conditions associated with over- or underproduction of this hormone. Recent work with genetically modified mice which are unable to produce oxytocin indicates that the hormone is essential for lactation, but not for parturition.
Oxytocin exemplifies interplay between hormonal and neural systems: unlike most hormones, it is made in nerve rather than glandular cells. Sensory nerves stimulate the nerve cells to activate its extrusion into the blood so that — like other hormones — it reaches the ‘target’ site via the circulation. This is an example of a ‘neuroendocrine’ secretion.
— Mary L. Forsling
See also birth; breast; hormones; infant feeding; pituitary.
Drug Info:
Oxytocin |
Brand names: Pitocin®
Chemical formula:

Oxytocin injection
What is oxytocin injection?
What should I tell my health care provider before I take this medicine?
They need to know if you have any of these conditions:
breech, placenta previa, or other abnormal position of the fetus or umbilical cord
cervical cancer
eclampsia
herpes infection
more than 7 pregnancies
premature delivery
previous uterine surgery (including cesarean section)
prolapsed uterus
an unusual or allergic reaction to oxytocin, other medicines, foods, dyes, or preservatives
How should I use this medicine?
Oxytocin is for injection into a muscle or infusion into a vein. It is given by a health-care professional in a hospital or clinic setting where uterine contractions, mother's blood pressure and mother's and baby's heart rates can be monitored regularly, and where emergency measures can be taken immediately, if needed.
What drug(s) may interact with oxytocin?
Oxytocin can interact with some other medicines. Your condition will be carefully monitored while you receive oxytocin.
Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Check with your health care professional before stopping or starting any of your medicines.
What should I watch for while taking oxytocin?
Your condition will be closely monitored while you receive oxytocin.
What side effects may I notice from receiving oxytocin?
Side effects with oxytocin are rare. Serious side effects with oxytocin include:
chest pain or difficulty breathing
confusion
difficulty passing urine, sudden weight gain
excessive or continuing vaginal bleeding
fast or irregular heartbeat (palpitations)
seizures (convulsions)
severe or continuing headaches
skin rash or itching (hives)
unusual swelling
Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
irritation at the injection site
nausea and vomiting
Where can I keep my medicine?
This medication is only given in a hospital or clinic. You will not keep this medicine at home.
Last updated: 7/1/2002
Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.
Oxford A-Z of Medicinal Drugs:
oxytocin |
| oxytetracycline, oxymetazoline, oxycodone | |
| paclitaxel, paint, palifermin |
Columbia Encyclopedia:
oxytocin |
Oxford Dictionary of Biochemistry:
oxytocin |
| oxytetracycline, oxysterol receptor, oxysome | |
| oxytocin receptor, oz, ozone |
Saunders Veterinary Dictionary:
oxytocin |
A hypothalamic hormone stored in and released from the posterior pituitary, or prepared synthetically. Produced also by the corpus luteum of sheep, and perhaps other animals. Involved in the release of PGF2α which induces luteolysis. It acts as a powerful stimulant to the pregnant uterus, especially toward the end of gestation. The hormone also causes milk to be expressed from the alveoli into the lactiferous ducts during suckling.
Mosby's Dental Dictionary:
oxytocin |
A hormone of the posterior pituitary gland that is the principal uterus-contracting hormone. Used in obstetrics to induce uterine contractions.
Random House Word Menu:
categories related to 'oxytocin' |

Rhymes:
oxytocin |
Wikipedia on Answers.com:
Oxytocin |
| Systematic (IUPAC) name | |
|---|---|
| 1-({(4R,7S,10S,13S,16S,19R)-19-amino-7-(2-amino-2-oxoethyl)-10-(3-amino-3-oxopropyl)-16-(4-hydroxybenzoyl)-13-[(1S)-1-methylpropyl]-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentaazacycloicosan-4-yl}carbonyl)-L-prolyl-L-leucylglycinamide | |
| Clinical data | |
| Trade names | Pitocin |
| AHFS/Drugs.com | monograph |
| Pregnancy cat. | A(AU) |
| Legal status | POM (UK) ℞-only (US) |
| Routes | Intranasal, IV, IM |
| Pharmacokinetic data | |
| Bioavailability | nil |
| Protein binding | 30% |
| Metabolism | hepatic oxytocinases |
| Half-life | 1–6 min |
| Excretion | Biliary and renal |
| Identifiers | |
| CAS number | 50-56-6 |
| ATC code | H01BB02 |
| PubChem | CID 439302 |
| DrugBank | DB00107 |
| ChemSpider | 388434 |
| UNII | 1JQS135EYN |
| KEGG | D00089 |
| ChEBI | CHEBI:7872 |
| ChEMBL | CHEMBL265640 |
| Chemical data | |
| Formula | C43H66N12O12S2 |
| Mol. mass | 1007.19 g/mol |
| SMILES | eMolecules & PubChem |
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Oxytocin (Oxt) (
/ˌɒksɨˈtoʊsɪn/) is a mammalian hormone that acts primarily as a neuromodulator in the brain.
Oxytocin is best known for its roles in sexual reproduction, in particular during and after childbirth. It is released in large amounts after distension of the cervix and uterus during labor, facilitating birth, and after stimulation of the nipples, facilitating breastfeeding.
Recent studies have begun to investigate oxytocin's role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, and maternal behaviors.[1] For this reason, it is sometimes referred to as the "love hormone". The inability to secrete oxytocin and feel empathy is linked to sociopathy, psychopathy, narcissism and general manipulativeness.[2]
The word oxytocin was derived from the Greek ὼκυτοκίνη, ōkytokínē, meaning “quick birth”, after its uterine-contracting properties were discovered by British pharmacologist Sir Henry Hallett Dale in 1906.[3] The milk ejection property of Oxt was described by Ott and Scott in 1910[4] and by Schafer and Mackenzie in 1911.[5] The nine amino acid sequence of Oxt was elucidated by Vincent du Vigneaud et al. and by Tuppy in 1953.[6] and synthesized biochemically soon after by du Vigneaud et al. in 1953.[7][8] Oxytocin was the very first polypeptide hormone to be sequenced and synthesized.[citation needed]
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Contents
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Oxytocin is a peptide of nine amino acids (a nonapeptide). Its systematic name is cysteine-tyrosine-isoleucine-glutamine-asparagine-cysteine-proline-leucine-glycine-amine (cys – tyr – ile – gln – asn – cys – pro – leu – gly - NH2, or CYIQNCPLG-NH2). The cysteine residues form a disulfide bond. Oxytocin has a molecular mass of 1007 daltons. One international unit (IU) of oxytocin is the equivalent of about 2 micrograms of pure peptide.
The biologically active form of oxytocin, commonly measured by RIA and/or HPLC techniques, is also known as the octapeptide "oxytocin disulfide" (oxidized form), but oxytocin also exists as a reduced dithiol nonapeptide called oxytoceine.[9] It has been theorized that open chain oxytoceine (the reduced form of oxytocin) may also act as a free radical scavenger (by donating an electron to a free radical); oxytoceine may then be oxidized back to oxytocin via the redox potential of dehydroascorbate <---> ascorbate.[10]
The structure of oxytocin is very similar to that of vasopressin (cys – tyr – phe – gln – asn – cys – pro – arg – gly - NH2), also a nonapeptide with a sulfur bridge, whose sequence differs from oxytocin by 2 amino acids. A table showing the sequences of members of the vasopressin/oxytocin superfamily and the species expressing them is present in the vasopressin article. Oxytocin and vasopressin were isolated and synthesized by Vincent du Vigneaud in 1953, work for which he received the Nobel Prize in Chemistry in 1955.
Oxytocin and vasopressin are the only known hormones released by the human posterior pituitary gland to act at a distance. However, oxytocin neurons make other peptides, including corticotropin-releasing hormone (CRH) and dynorphin, for example, that act locally. The magnocellular neurons that make oxytocin are adjacent to magnocellular neurons that make vasopressin, and are similar in many respects.
Oxytocin has peripheral (hormonal) actions, and also has actions in the brain. The actions of oxytocin are mediated by specific, high-affinity oxytocin receptors. The oxytocin receptor is a G-protein-coupled receptor that requires Mg2+ and cholesterol. It belongs to the rhodopsin-type (class I) group of G-protein-coupled receptors.
The peripheral actions of oxytocin mainly reflect secretion from the pituitary gland. (See oxytocin receptor for more detail on its action.)
Oxytocin evokes feelings of contentment, reductions in anxiety, and feelings of calmness and security around the mate.[20] Many studies have already shown a correlation of oxytocin with human bonding, increases in trust, and decreases in fear. One study confirmed that there is a positive correlation between oxytocin plasma levels and an anxiety scale measuring the adult romantic attachment.[21] This suggests that oxytocin may be important for the inhibition of brain regions that are associated with behavioral control, fear, and anxiety, thus allowing orgasm to occur.
Oxytocin secreted from the pituitary gland cannot re-enter the brain because of the blood-brain barrier. Instead, the behavioral effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland, or that are collaterals from them.[47] Oxytocin receptors are expressed by neurons in many parts of the brain and spinal cord, including the amygdala, ventromedial hypothalamus, septum, nucleus accumbens, and brainstem.
Synthetic oxytocin is sold as proprietary medication under the trade names Pitocin and Syntocinon and also as generic oxytocin. Oxytocin is destroyed in the gastrointestinal tract, and therefore must be administered by injection or as nasal spray. Oxytocin has a half-life of typically about three minutes in the blood. Oxytocin given intravenously does not enter the brain in significant quantities - it is excluded from the brain by the blood-brain barrier. There is no evidence for significant central nervous system entry of oxytocin by nasal spray. Oxytocin nasal sprays have been used to stimulate breastfeeding but the efficacy of this approach is doubtful.[60]
Injected oxytocin analogues are used for labor induction and to support labor in case of non-progression of parturition. It has largely replaced ergometrine as the principal agent to increase uterine tone in acute postpartum hemorrhage. Oxytocin is also used in veterinary medicine to facilitate birth and to stimulate milk release. The tocolytic agent atosiban (Tractocile) acts as an antagonist of oxytocin receptors; this drug is registered in many countries to suppress premature labor between 24 and 33 weeks of gestation. It has fewer side-effects than drugs previously used for this purpose (ritodrine, salbutamol, and terbutaline).
Some have suggested that the trust-inducing property of oxytocin might help those who suffer from social anxieties and mood disorders,[44] while others have noted the potential for abuse with confidence tricks[61][62] and military applications.[63]
Oxytocin is relatively safe when used at recommended doses, and side-effects are uncommon.[64] The following maternal events have been reported:[64]
Excessive dosage or long term administration (over a period of 24 hours or longer) have been known to result in tetanic uterine contractions, uterine rupture, postpartum hemorrhage, and water intoxication, sometimes fatal.
Increased uterine motility has led to the following complications in the fetus/neonate:[64]
In addition, use of pitocin in the mother has been associated with neonatal jaundice, retinal hemorrhage, and low five-minute Apgar score.
Oxytocin can be administered to bovine animals in order to increase the production of dairy milk.[citation needed]
The oxytocin peptide is synthesized as an inactive precursor protein from the OXT gene.[65][66][67] This precursor protein also includes the oxytocin carrier protein neurophysin I.[68] The inactive precursor protein is progressively hydrolyzed into smaller fragments (one of which is neurophysin I) via a series of enzymes. The last hydrolysis that releases the active oxytocin nonapeptide is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM).[69]
The activity of the PAM enzyme system is dependent upon ascorbate, which is a necessary vitamin cofactor. By chance, it was discovered that sodium ascorbate by itself stimulated the production of oxytocin from ovarian tissue over a range of concentrations in a dose-dependent manner.[70] Many of the same tissues (e.g. ovaries, testes, eyes, adrenals, placenta, thymus, pancreas) where PAM (and oxytocin by default) is found are also known to store higher concentrations of vitamin C.[71]
In the hypothalamus, oxytocin is made in magnocellular neurosecretory cells of the supraoptic and paraventricular nuclei and is stored in Herring bodies at the axon terminals in the posterior pituitary. It is then released into the blood from the posterior lobe (neurohypophysis) of the pituitary gland. These axons (likely, but dendrites have not been ruled out) have collaterals that innervate oxytocin receptors in the nucleus accumbens.[47] The peripheral hormonal and behavioral brain effects of oxytocin it has been suggested are coordinated through its common release through these collaterals.[47] Oxytocin is also made by some neurons in the paraventricular nucleus that project to other parts of the brain and to the spinal cord.[72] Depending on the species, oxytocin-receptor expressing cells are located in other areas, including the amygdala and bed nucleus of the stria terminalis.
In the pituitary gland, oxytocin is packaged in large, dense-core vesicles, where it is bound to neurophysin I as shown in the inset of the figure; neurophysin is a large peptide fragment of the larger precursor protein molecule from which oxytocin is derived by enzymatic cleavage.
Secretion of oxytocin from the neurosecretory nerve endings is regulated by the electrical activity of the oxytocin cells in the hypothalamus. These cells generate action potentials that propagate down axons to the nerve endings in the pituitary; the endings contain large numbers of oxytocin-containing vesicles, which are released by exocytosis when the nerve terminals are depolarised.
Outside the brain, oxytocin-containing cells have been identified in several diverse tissues including the corpus luteum,[73][74] the interstitial cells of Leydig,[75] the retina,[76] the adrenal medulla,[77] the placenta,[78] the thymus[79] and the pancreas.[80] The finding of significant amounts of this classically "neurohypophysial" hormone outside the central nervous system raises many questions regarding its possible importance in these different tissues.
Oxytocin is synthesized by corpora lutea of several species, including ruminants and primates. Along with estrogen, it is involved in inducing the endometrial synthesis of prostaglandin F2α to cause regression of the corpus luteum.
The Leydig cells in some species have also been shown to possess the biosynthetic machinery to manufacture testicular oxytocin de novo, to be specific, in rats (which can synthesize Vitamin C endogenously), and in guinea pigs, which, like humans, require an exogenous source of vitamin C (ascorbate) in their diets.[81]
The oxytocin receptor in humans has several alleles, which differ in their effectiveness. Individuals homozygous for the "G" allele, when compared to carriers of the "A" allele, show higher empathy, lower stress response,[82] as well as lower prevalence of autism and of poor parenting skills.[83]
Virtually all vertebrates have an oxytocin-like nonapeptide hormone that supports reproductive functions and a vasopressin-like nonapeptide hormone involved in water regulation. The two genes are usually located close to each other (less than 15,000 bases apart) on the same chromosome and are transcribed in opposite directions (however, in fugu,[84] the homologs are further apart and transcribed in the same directions).
It is thought that the two genes resulted from a gene duplication event; the ancestral gene is estimated to be about 500 million years old and is found in cyclostomata (modern members of the Agnatha).[36]
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
| neurohypophyseal hormones | |
| Pitocin (trademark) | |
| What are the functions of oxytocin? (anatomy) |
| What does the hormone oxytocin do? Read answer... | |
| What is hormone oxytocin? Read answer... | |
| What is the antidote for oxytocin? Read answer... |
| Oxytocin is secreted by? | |
| What are the receptors of oxytocin? | |
| What does oxytocin regulate? |
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![]() | American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
![]() | Word Overheard by Answers.com. © 1999-present by Answers Corporation. All rights reserved. Read more | |
![]() | Oxford Companion to the Body. The Oxford Companion to the Body. Copyright © 2001, 2003 by Oxford University Press. All rights reserved. Read more | |
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| Oxford A-Z of Medicinal Drugs. Market University Press. © 2000, 2003, 2010 An A-Z of Medicinal Drugs. All rights reserved. Read more | ||
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![]() | Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2012, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
| Oxford Dictionary of Biochemistry. Oxford University Press. Oxford Dictionary of Biochemistry and Molecular Biology © 1997, 2000, 2006 All rights reserved. Read more | ||
![]() | Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more | |
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