Scientific Reference
Oxytocin
Evidence profile: Controlled human evidence
Oxytocin is a nine-residue peptide hormone, cyclised by a disulphide bond between its two cysteines and amidated at the C-terminus. It is made by neurons of the hypothalamus and released both from the posterior pituitary into the circulation and within the brain. It differs from vasopressin at two of its nine positions, and their receptors belong to one family. Its classical physiological roles, in uterine contraction and milk ejection, were established first, and in the 1950s it became the first peptide hormone to be synthesised in the laboratory. More recent research concerns its signalling in the brain and social behaviour; the animal literature is substantial, while human findings have been inconsistent and remain debated.
Mechanism of Action
The oxytocin receptor (OXTR) is a class A G-protein-coupled receptor that signals mainly through Gq/11, activating phospholipase C and raising intracellular calcium; coupling to other G proteins has also been reported. It is expressed in the myometrium, mammary myoepithelial cells and several brain regions, among other tissues, and uterine expression rises sharply late in pregnancy. Because oxytocin and vasopressin are so alike, each can act at the other's receptors at higher concentrations, and oxytocin has measurable activity at the vasopressin V1a receptor. How much oxytocin in the circulation crosses into the brain is still debated.
Molecular Information
- Type: Cyclic nonapeptide hormone (neurohypophysial peptide)
- Length: 9 amino acids
- Molecular weight: 1007.2 g/mol
- Molecular formula: C43H66N12O12S2
- CAS: 50-56-6
Pharmacokinetics
Plasma half-life of oxytocin ranges from 3 to 20 min.
Published Research
Impact of chronic intranasal oxytocin administration on face expression processing in autistic children: a randomized controlled trial using fMRI
Moerkerke M et al. · Molecular autism · 2024 · Clinical
PMID 39709442 — View on PubMedA randomized controlled trial examining the effects of intranasal oxytocin on alcohol craving and intimate partner aggression among couples
Flanagan JC et al. · Journal of psychiatric research · 2022 · Clinical
PMID 35709548 — View on PubMedHigh- vs low-dose oxytocin protocols for labor induction: a systematic review and meta-analysis
Grasch JL et al. · American journal of obstetrics & gynecology MFM · 2025 · Review
PMID 40334983 — View on PubMedReduced risk of cesarean delivery with oxytocin discontinuation in active labor: a systematic review and meta-analysis
Whitley J et al. · American journal of obstetrics and gynecology · 2025 · Review
PMID 40113155 — View on PubMedOxytocin and vaginal dinoprostone in labor induction: A systematic review and meta-analysis
Chang TA et al. · International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics · 2024 · Review
PMID 38404054 — View on PubMedAssociation of oxytocin augmentation with postpartum hemorrhage: a systematic review and meta-analysis
Jafarabady K et al. · The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians · 2024 · Review
PMID 38910114 — View on PubMed