DRPSHP

Scientific Reference

Oxytocin

Evidence profile: Controlled human evidence

Oxytocin was the first peptide hormone anyone synthesised in a laboratory, in the 1950s, by which point its classical physiology — uterine contraction and milk ejection — was already established. It is nine residues, closed into a ring by a disulphide bond between its two cysteines and amidated at the C-terminus, made by hypothalamic neurons and released both into the circulation from the posterior pituitary and directly within the brain. Two of those nine positions are all that separate it from vasopressin, and the two hormones' receptors belong to a single family. The newer literature has moved to brain signalling and social behaviour, where the animal work is substantial but human findings have been inconsistent and are still argued over.

Mechanism of Action

The oxytocin receptor is a class A G-protein-coupled receptor signalling principally through Gq/11: phospholipase C is activated and intracellular calcium rises, though coupling to other G proteins has been reported too. It is found in the myometrium, in mammary myoepithelial cells and in a number of brain regions among other tissues, and uterine expression climbs steeply in late pregnancy. The close resemblance between oxytocin and vasopressin cuts both ways — at higher concentrations each can act at the other's receptors, and oxytocin has measurable activity at the vasopressin V1a receptor. How much circulating oxytocin reaches the brain at all remains a matter of debate.

Molecular Information

  • Type: Cyclic nonapeptide hormone (neurohypophysial peptide)
  • 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 PubMed

  • A 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 PubMed

  • High- 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 PubMed

  • Reduced 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 PubMed

  • Oxytocin 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 PubMed

  • Association 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