Oxytocin - The Love Hormone?

by Tiffany Spudich, Pharm.D.
November 2008

(brought to you by Bellevue Pharmacy, a ProjectAWARE sponsor)

Oxytocin, sometimes called the hormone of love, not only induces uterine contractions during childbirth but is also released as a mother nurses her baby and is responsible, at first touch, for her feelings of attachment to the newborn. The instinct to want to cuddle continues to intensify; hence oxytocin often also gets referred to as the “cuddle hormone.” Oxytocin was first synthesized in 1951 and has been prescribed to women since then to induce labor and facilitate breast-feeding. Oxytocin means "swift birth" in Greek.

But the role of oxytocin goes beyond childbirth and mother-infant bonding. Oxytocin, found in both men and women, has a large role in promoting enduring friendships, marriages, and relationships. It is even suggested that it can even promote trust among strangers. Data has shown that oxytocin reduces anxiety levels in users and hence helps to facilitate social contact between people. One study by Paul Zak, PhD, of Claremont University, and colleagues found that following administration of oxytocin through a nasal spray, study participants were more generous toward strangers and trusted them much more than those who did not receive oxytocin.(1) Data has also demonstrated that participants who were given an oxytocin infusion gave significantly more money to a stranger than participants who took a placebo.(2)

The primary conscious behavior or thought process that increases oxytocin is caring for another. Appreciation, generous touch, gratitude, and emotional connections with others also raise oxytocin levels. As with a mom and her baby, oxytocin is released in the brain in response to hugs, kisses, and caresses, as well as simple touching. A hug prompts the release of oxytocin, leading to feelings of closeness, sexual intimacy, and the release of more oxytocin. Oxytocin's role in sexual response is primarily to facilitate attraction and touch sensation, with levels increasing secondary to touch and spiking during orgasm.(3) Orgasm generally produces a spike in the hormone more than two times the normal level, accounting for the calming postcoital afterglow and greater bonding.

Oxytocin has peripheral hormonal actions and also has actions in the brain. The peripheral actions of oxytocin mainly reflect secretion from the pituitary gland, including lactation and uterine contractions. Oxytocin secreted from the pituitary gland cannot re-enter the brain because of the blood-brain barrier. Instead, the behavioral effects of oxytocin are thought to reflect release from centrally projecting oxytocin neurons, different from those that project to the pituitary gland. These effects include sexual arousal, maternal behavior, bonding, and feelings such as trust and generosity.(4) One mechanism of oxytocin is that it binds to proteins embedded in the cell membrane of the amygdala, a ganglion of the limbic system adjoining the temporal lobe of the brain that is involved in emotions of fear and aggression. This binding activates neurotransmitters that inhibit cells in the amygdala, reducing neural activity. However, the exact length of oxytocin’s inhibitory effect is unknown. According to Ron Stoop of the Center for Psychiatric Neurosciences at the University of Lausanne, Switzerland, the effect of oxytocin appears to only be short-lived.(1) This could be due to the fact that oxytocin itself is quickly metabolized and eliminated from the body.

Experimental studies in animals, as well as case reports in humans, suggest that oxytocin affects different aspects of sexual behavior and has predominantly facilitating properties for sexual appetence and performance. One double-blind, placebo-controlled study showed that intranasally administered oxytocin leads to a marked increase in oxytocin levels in the blood with increased secretion of epinephrine when subjects were engaged in sexual activity in a laboratory setting.(5) Also, one case report presented the case of treatment-resistant male anorgasmia who was successfully treated with administration of intranasal oxytocin during intercourse.(6)

Oxytocin may also play a role in autism and may be a treatment option for autism’s repetitive and affiliative behaviors.(7) Two related studies in adults, in 2003 and 2007, found that oxytocin decreased repetitive behaviors and improved interpretation of emotions, but these preliminary results do not necessarily apply to children.(8) In the future, oxytocin could eventually be considered for treatment of social disorders characterized by excessive fear, such as social phobia, autism and post-traumatic stress disorder. However, treatments for social disorders must help increase the person’s desire to interact with others, not just increase their likelihood to trust.

The effects of this natural “love hormone” are amplified by estrogen, which is one reason women often tend to be more physically demonstrative than men and are generally affected more by touch. It has been suggested also that stress can restrain the production of oxytocin.(9) Drug effects on oxytocin are not well established, but estrogen and yohimbine increase its levels and alcohol decreases them.(3)

Oxytocin has been investigated in limited studies that were generally using a small study population. Paul Zak, PhD, a neuro-economist at Claremont University who has been directly involved with many of the studies regarding the neural activity of oxytocin and its influences economic decisions, says it is premature to speculate on clinical uses of oxytocin. Many studies have only evaluated its effects on men, and since oxytocin has a role in breastfeeding and childbirth, it is important to determine whether the hormone has a different effect on women.(1) This therapy is not yet specifically indicated for treatment of autism, social disorders, or sexual responsiveness in either gender.

Patients with congestive failure or decreased renal function are not good candidates for oxytocin therapy, because of its propensity to cause fluid retention. Oxytocin helps to stimulate micro-circulation, thereby potentially increasing body temperature which can make some patients feel warm.(9) Oxytocin can also cause headache, an increase in blood pressure, and a decrease in heart rate. Oxytocin is destroyed in the gastrointestinal tract, so it is generally administered by injection, nasal spray, or sublingual dosage form. Bellevue Pharmacy currently compounds both oxytocin sublingual tablets and oxytocin nasal spray, which require a prescription.

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