# Oxytocin > A 9-amino-acid cyclic hormone of labor and bonding — historically the first peptide hormone ever chemically synthesized, and the most over-marketed "love hormone." - Also known as: Pitocin, Syntocinon, the love hormone - Class: Reproductive, Cognitive - FDA approved: Yes - Canonical page: https://www.americanpeptide.com/catalog/oxytocin ## Overview Oxytocin is a tiny but pivotal hormone: a 9-amino-acid cyclic peptide, closed by a single disulfide bridge, released from the posterior pituitary. It drives uterine contractions in labor and milk letdown in nursing, and it acts in the brain on social behavior — the source of its "love hormone" fame. It also holds a place in scientific history: in 1953 Vincent du Vigneaud synthesized it, the first polypeptide hormone ever made in the lab, a feat that won the 1955 Nobel Prize in Chemistry and opened the door to synthetic peptide therapeutics. Oxytocin’s established medicine is obstetric. As Pitocin it is one of the most widely used drugs in childbirth — to induce or augment labor and to control bleeding afterward — and it mediates the milk-ejection reflex during breastfeeding. Structurally it is almost a twin of vasopressin, differing in only two residues, which is why the two hormones’ effects sometimes overlap. Its fame, though, comes from the brain. Animal and early human work tied oxytocin to pair-bonding, maternal behavior, trust, and social affiliation, and the popular press crowned it the "love hormone" or "cuddle chemical." That framing drove a wave of intranasal-oxytocin research and products promising better social functioning — in autism, social anxiety, even relationship enhancement. The honest reckoning is more sober. Rigorous, larger trials of intranasal oxytocin — including in autism — have largely failed to reproduce the early promise, and there are real questions about how much intranasal oxytocin even reaches the brain. Oxytocin is a genuine, important hormone whose behavioral marketing ran far ahead of the evidence — a textbook case of a misunderstood molecule, which is exactly why it belongs in an honest reference. ## Mechanism Agonist at the oxytocin receptor (a G-protein-coupled receptor). Peripherally it contracts uterine smooth muscle and the mammary myoepithelium; centrally it modulates circuits involved in social bonding, trust, and stress, which is the basis of its behavioral research. ## Chemistry | Property | Value | | --- | --- | | Molecular formula | C43H66N12O12S2 | | Molecular weight | 1007.19 Da | | CAS number | 50-56-6 | ## Sequence ``` CYIQNCPLG-NH2 ``` ## Research areas Studied in: Labor induction, Lactation, Social bonding, Anxiety and stress. Guides on this site: - [Anxiety, Mood & Stress](https://www.americanpeptide.com/research-areas/anxiety-mood): Regulatory peptides studied for anxiolysis and stress-axis modulation. ## Key research - Labor and delivery — induction/augmentation of labor and control of postpartum bleeding (the core approved use). - Lactation — mediates the milk-ejection (letdown) reflex. - Social neuroscience — studied for bonding, trust, and stress modulation; the basis of the "love hormone" label. - Intranasal hype vs evidence — larger trials (including autism) have largely not confirmed early behavioral claims. - A historic first — the first peptide hormone chemically synthesized (du Vigneaud, 1953; Nobel Prize 1955). ## Storage, handling & synthesis **Storage.** Oxytocin injection is stored refrigerated (2–8 °C) per most labels; the cyclic disulfide peptide is sensitive to heat over time. Nasal/compounded forms follow their own storage. **Handling.** A small disulfide-bridged peptide; protect from heat and prolonged storage in solution to preserve potency. **Synthesis.** Oxytocin is a 9-residue cyclic peptide with a single intramolecular disulfide bond, made by solid-phase peptide synthesis — fittingly, since its 1953 chemical synthesis was the historical proof that peptide hormones could be built in the lab at all. Its small size and defined structure make it straightforward to characterize by mass spectrometry and HPLC, unlike the large folded biologics elsewhere in this catalog. ## FAQs ### What is oxytocin? A 9-amino-acid cyclic hormone from the posterior pituitary that drives uterine contractions and milk letdown, and acts in the brain on social behavior. As a drug (Pitocin) it is used in labor. ### Is oxytocin really the "love hormone"? It does play a role in bonding and social behavior, but the "love hormone" label is overstated. Rigorous trials of intranasal oxytocin for social conditions, including autism, have largely failed to confirm the early hype. ### Why is oxytocin historically important? It was the first peptide hormone ever chemically synthesized (Vincent du Vigneaud, 1953), which won the 1955 Nobel Prize in Chemistry and helped launch the field of synthetic peptide therapeutics. ### Is this medical advice? No — this is a research and educational reference, not dosing guidance. ## Latest research Recent trials and publications mentioning Oxytocin, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [Music for Pain and Dementia](https://clinicaltrials.gov/study/NCT07602283) — RECRUITING · NA · NCT07602283 - [Social Safety Learning in the Brain Oxytocin System](https://clinicaltrials.gov/study/NCT05968651) — COMPLETED · PHASE2 · NCT05968651 - [Recovery Rate From Category II to Category I EFM Tracings in Pregnant Women Receiving Bolus vs Continuous Intravenous Fluid Administration](https://clinicaltrials.gov/study/NCT07260240) — COMPLETED · NA · NCT07260240 - [Carbetocin Monotherapy Versus Carbetocin Plus Oxytocin Infusion in Elective Cesarean Delivery: A Non-Inferiority Trial](https://clinicaltrials.gov/study/NCT07636421) — NOT_YET_RECRUITING · PHASE4 · NCT07636421 - [Effects of Dim Light During Labor on Pain, Anxiety, and Labor Progress](https://clinicaltrials.gov/study/NCT07310602) — COMPLETED · NA · NCT07310602 - [Positive Expectation Effects on Early Emotional Processing](https://clinicaltrials.gov/study/NCT07615530) — NOT_YET_RECRUITING · NA · NCT07615530 --- Source: AmericanPeptide.com — https://www.americanpeptide.com/catalog/oxytocin Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.