Oxytocin is a hormone that is made in the brain, in the hypothalamus, and it is transported to, and secreted by, the pituitary gland, which is located at the base of the brain.
Chemically it is known as a nonapeptide (a peptide containing nine amino acids), and biologically, as a neuropeptide. It acts both as a hormone and as a brain neurotransmitter.
1. Child birth
The release of the hormone during labor makes the muscles of the uterus, womb, contract - in other words, it increases uterine motility. The release of oxytocin is triggered by the widening of the cervix and vagina during labor, and this effect is in turn increased by the subsequent contractions.3
The main role of oxytocin is summed up nicely in a research paper by obstetric and gynecology specialists Navneet Magon and Sanjay Kalra:2
"It is released in large amounts during labor, and after stimulation of the nipples. It is a facilitator for childbirth and breast-feeding."
2. Breast-feeding.
Stimulation of the nipples results in oxytocin release and milk let-down.
Other researchers sum up the reproductive importance of oxytocin by saying it "serves the continued propagation of a species," adding that through evolution its "repertoire has expanded to maintain a central role in more complicated aspects of reproductive behavior. For these reasons, we call oxytocin the great facilitator of life."
Doctors prescribe oxytocin to start birth contractions or strengthen them during labor. It is also used to reduce bleeding after child delivery.4,5 The drug also has a role in the medical termination of pregnancy or during miscarriage.5
Oxytocin's effects on emotion
Oxytocin is released into the bloodstream to produce its classic effects on the uterus and breast milk, but it is also released into defined regions of the brain that are involved in emotional, cognitive, and social behaviors.
One review of the evidence says oxytocin "has attracted intense attention" after the discovery of its "amazing variety of behavioral functions."
The review, by Inga Neumann, says oxytocin has an impact on "pro-social behaviors" and emotional responses that contribute to:
However, another review notes that the hormone does not act alone in the chemistry of love, but is "just one important component of a complex neurochemical system that allows the body to adapt to highly emotive situations."7
Male and female embrace
Oxytocin has been the focus of research into the biology of love.
Another review has also sounded caution, calling for research to look more to the general effects than to the specific effects of oxytocin that are being interpreted.
"After all, it is rather unlikely that any widely acting hormone or neurotransmitter will be narrowly funneled to modulate complex, high-order mental processes that are specific to social cognition," say the authors of a 2013 paper.8
Scientific research has nonetheless uncovered brain oxytocin's specific ability to modulate social behavior, including effects on motherly care and aggression, bonding between couples, sexual behavior, social memory, and trust.6
Brain oxytocin also reduces stress responses, including anxiety - and these anxiolytic effects have been demonstrated in a number of species.6,8
One of the so-called 'love hormone' studies was published in 2012, and it examined oxytocin levels in new lovers versus those in single people. It found that there were high levels of the hormone in the first stages of romantic attachment, and these were sustained for six months
