The Powers of Oxytocin, from Pregnancy to Social Attachment

Discovered by Sir Henry Dale in the context of its role in childbirth, oxytocin revealed its secrets over the years. This hormone, essential to human life (including men!), has a diversity of activities that continue to surprise.

Discovered through childbirth

The name oxytocin comes from two words in ancient Greek, "ōkus" and "tokos," meaning "swift" and "birth," respectively. This term, adopted by the English researcher Sir Henry Dale in 1906, refers to the first role he discovered for it: inducing the contraction of the smooth muscles of the uterus during childbirth.

It is a neurohormone, meaning a hormone synthesized by neurons located in the hypothalamus, a small structure at the base of the brain. It is released into the body to exert its actions at a distance through the communication of these neurons with fine blood vessels located in the neurohypophysis, a small gland nearby.

Fig. 1 : The human brain and location of the hypothalamus/pituitary gland (https://www.nursingtimes.net/clinical-archive/long-term-conditions/endocrine-system-2-hypothalamus-and-pituitary-gland-24-05-2021/)

It also has the ability to act in the nervous system as a neurotransmitter. Oxytocin acts by binding to specific receptors known as oxytocin receptors. They are located in various areas of the nervous system as well as in many organs (kidneys, heart, thymus, pancreas), and broadly in the digestive pathways. In women, specifically, they are found in the uterus and nipples. In men, they are located in the corpora cavernosa of the penis (the body that enables erection) and the epididymis (the organ that transports sperm from the testicles to the penis).

Code name: the love and attachment hormone

But there is no need to be pregnant and give birth to benefit from the effects of oxytocin. In our daily lives, this hormone acts in our brains to help initiate, facilitate, and strengthen social relationships. It has an anti-stress effect by regulating the secretion of two stress hormones (adrenocorticotropic hormone and cortisol). In humans, it increases both self-confidence and the trust inspired by others, two important parameters of social connection. It also helps us overcome the betrayal and regain trust in another person.

Once the relationship has begun, oxytocin enables the recognition of familiar individuals and contributes to improving the recognition of emotions displayed on the faces of our interlocutors. Then, a positive loop is established: the hypothalamus secretes oxytocin to promote social behaviors, which, in turn, increase its secretion. This loop is enriched by the reciprocal trust felt between individuals who maintain a social bond.

"But to live without tenderness, we could not do it"

The french singer Bourvil's interpretation of "La Tendresse" understood everything about the powers of oxytocin! As we know, physical contact and gestures of tenderness from loved ones promote a fulfilling life for most of us. And it's again thanks to oxytocin. Indeed, a small population of hypothalamic neurons called parvocellular oxytocinergic neurons receives information from physical contact and induces the release of oxytocin in the nervous system and in the blood to relax and strengthen social bonds. Oxytocin concentrations in the blood are thus correlated with the number of physical contacts such as hugs. In stressful situations, support or tender gestures can help through the stimulation of oxytocin synthesis. During various periods of COVID-19-related restrictions, the limitation of this phenomenon greatly contributed to the impact on the mental health of the population.

This effect of tenderness is reinforced in couples and in their sexuality since, as we have seen, oxytocin receptors are numerous in the female and male genital organs. Overall, whether for men or women, the high secretion of oxytocin induced by sexual intercourse and the activation of these receptors allow for achieving orgasm and ultimately strengthen the attachment between partners.

The key to harmonious childbirth and maternal attachment

Beyond its effect on sexuality, the presence of numerous oxytocinergic receptors in the walls of the uterus and in the nipples has established oxytocin as the conductor of the smooth progress of childbirth and subsequently breastfeeding.

Fig. 2 : The positive birth loop (From J’accouche bientôt. Que faire de la douleur ? Maïtie Trelaün, 2008)

In the same way as in social relationships, oxytocin will generate a virtuous circle to facilitate childbirth. At the beginning of the childbirth process, oxytocin is released in small quantities, causing mild uterine contractions. The oxytocin level will gradually increase because oxytocin calls for more oxytocin. Paradoxically, the hormone's increase will both intensify contractions and induce a sense of relaxation. In parallel, this will trigger the production of endorphins, naturally pain-relieving and relaxing molecules between contractions, helping the expectant mother to let go. This triggers a new release of oxytocin for another wave of contractions but also relaxation. By optimizing relaxation and contractions, the mother optimizes her oxytocin secretion and the physiology of her childbirth. However, it's not always as simple, and pain or anxiety can take over, preventing this hormonal dance and complicating the baby's birth.

Once the child is born, the levels of oxytocin in the mother's blood are normally very high. This has the effect, in addition to relaxing her, of facilitating the initiation of breastfeeding by optimizing the milk ejection to nourish the newborn immediately after birth. Subsequently, during breastfeeding, the mother experiences a surge of oxytocin that relaxes her, strengthens the bond with her child, and promotes breastfeeding.

The miracle hormone in the service of medicine?

In addition to its use in synthetic form to induce labor when pregnancy takes an undesirable turn (risk for the baby or the mother, overdue term, etc.), oxytocin has multiple therapeutic potentialities.

Oxytocin is very weakly synthesized in patients with autism or those with depression-anxiety or generalized anxiety. Researchers have shown that in certain autistic patients, the intake of oxytocin could notably improve their emotional perception of their surroundings and increase their self-confidence and trust in others. Improvement in emotional perception through oxytocin treatment is also observed in schizophrenic patients. In some studies, these patients have shown an overall favorable outcome after treatment. Therapeutic trials are also being conducted in the context of obesity and diabetes, as oxytocin plays a role in glucose metabolism, thermoregulation, energy expenditure, and bone maintenance.

A bit of a jack-of-all-trades, oxytocin is one of the most beneficial hormones for our well-being and mental health. It is the hormone that allows us to create connections, whether with others or with oneself, with one's baby, or between partners. Numerous research efforts must be continued to explore the full physiological and therapeutic potential of this hormone.