The Science of Sex and Love

Valentine’s Day means flowers, massage, and POETry. Referring to prolactin, oxytocin, estrogen, and testosterone, of course.

All 4 of those “love hormones” play key roles in romance and sexual function for both women and men, according to 2 experts with The Endocrine Society.

Clinicians can play an important role in helping patients understand how these hormones influence our bodies and our psyches, suggested Nanette Santoro, MD, and Bradley D. Anawalt, MD, following a webinar sponsored by the society. In fact, clinicians can help patients who are experiencing difficulties that might prevent them from celebrating Valentine’s Day the way they would like to, they offered.

Taking a sexual history is important in evaluating menopausal women, because many have issues but may hesitate to raise them with their clinician on their own, noted Dr. Santoro, Professor and E. Stewart Taylor Chair of Obstetrics and Gynecology at the University of Colorado at Denver. Clinicians may be similarly reluctant to start the discussion.

“Many physicians feel ‘trapped’ by these questions precisely because the patient is bashful about bringing it up, and thus it presents itself as a last-minute issue as the doctor literally has his or her hand on the office doorknob: ‘Oh, by the way…’,” she explained.

Dr. Santoro suggests that clinicians either ask the simple question “Are you satisfied with your sex life?” or use the Female Sexual Function Index, an easy-to-administer questionnaire available online.
For men, physicians increasingly are asking them about erectile dysfunction, and patients increasingly are willing to share that information, according to Dr. Anawalt. Loss of libido, however, is addressed less often.

“Male sexuality is not just about erections,” he said during the webinar, noting that high testosterone levels do not correlate with sexual function. However, he explained, small decreases in testosterone can affect sexual desire and satisfaction, as can visual cues and relationship issues.

“Low testosterone levels are seldom the cause for erectile dysfunction,” Dr. Anawalt said. “Total testosterone levels must be very low (< 150 ng/dL) before erectile function is affected, and even then, many men still have normal erections. They just lack sexual desire.”

In fact, estrogen is actually more important to normal male sexual function than previously realized, [2,3]  Dr. Anawalt noted. This recent finding could have important implications for men being treated with hormonal suppression for prostate cancer.

In the end, though, estrogen and testosterone “provide the fuel but not the fire,” he said. In other words, no hormone alone can spark mutual attraction in a couple if it’s not there to begin with.

The Chemistry of Women’s Desire

Estrogen and testosterone are not the only hormones involved in female sexuality, Dr. Santoro noted. Prolactin, the “hormone of lactation,” generally has no effect on libido in normally cycling women, but it can suppress sexual desire when levels are too high, such as in women who are breastfeeding, have prolactin-producing tumors, or are taking medications that affect dopamine pathways.

“[Prolactin is] one hormone that I think is little known but may have a profound effect on desire,” Dr. Santoro said. “I think it needs to be thought about in an endocrine setting.”

Oxytocin, the “cuddly hormone,” induces uterine contractions and facilitates milk ejection after childbirth. Elevated levels appear during orgasm, but its role in female sexual desire isn’t as clear as it is in men. Indeed, oxytocin has been linked with both enhanced and diminished sexual desire in women. [4,5]

Estrogen directly affects vaginal engorgement and lubrication, and it regulates female genital tissues’ “receptivity” to sexual activity. Until recently, estrogen was the only treatment for vaginal dryness and painful intercourse, problems that reportedly affect 30%-40% of postmenopausal women. In February 2013, the US Food and Drug Administration (FDA) approved the novel selective estrogen receptor modulator ospemifene as the first nonestrogen therapy for moderate to severe dyspareunia in postmenopausal women.

“It’s a very welcome thing, because there are many women out there who can’t take estrogen. You want to give them an alternative, but we had nothing except for lubricants and moisturizers, and they don’t always work,” Dr. Santoro said.
Some evidence suggests that testosterone also correlates with female sexual desire and satisfaction. [6,7]  Nonetheless, the FDA has been reluctant to approve the testosterone patch for women because the long-term safety isn’t known, Dr. Santoro noted. [8]

Moreover, no drug is likely to address all of the issues that affect female sexuality. “Context may mean a great deal, Dr. Santoro said. “In a lot of the models of female sexuality…relationship issues seem to have a bigger role. More than any of these hormones, in other studies of women and sexuality, the quality of their relationships dictates how sexual function plays out.”

In the clinical setting, she advised, a woman who responds affirmatively when asked about sexual problems should be questioned further about the specifics of the problem, as well as about relationship issues and whether she has experienced past sexual abuse.

“Women who are survivors of sexual abuse can have sexual problems crop up at seemingly illogical times of life — menopause being one of them — and the problem can play out as pelvic pain and other issues that lead to sexual aversion,” Dr. Santoro said.

Referral to a sex therapist can be helpful for patients in whom hormonal abnormalities have been ruled out, she added.

Poetry in Men

Hormones play different roles in male sexuality, Dr. Anawalt explained. Prolactin is the “stop” hormone, oxytocin the “soul mate” hormone, estrogen the “Adam’s rib of male sexuality,” and testosterone “the hormone of desire.”

When men engage in sex with a partner, blood concentrations of prolactin increase to a greater degree than in men who experience orgasm through masturbation, Dr. Anawalt said. Prolactin likely is responsible for the immediate decline in sexual desire and the onset of sleepiness following orgasm. “Prolactin may be an indicator of satiety,” he said.

Chronic elevations in prolactin can create a permanent “stop mode” by reducing blood testosterone and estrogen levels. This would explain the reduced sexual desire that often accompanies medications such as antidepressants or antipsychotics which suppress pituitary hormonal regulation, he noted.
Oxytocin appears to have more “subtle, nuanced” effects on male behavior. Several recent studies document the hormone’s effects on the emotional aspects of male sexuality. For example, administration of intranasal oxytocin increased the physical distance between men with monogamous partners and other women, but it did not have that effect on single men. [9]  Men given oxytocin also rated their female partners as more attractive compared with unfamiliar women. [10]

Other recent studies suggest that oxytocin in men increases their empathy for and speed of response to facial expression cues [11] ; increases activity in brain areas associated with arousal, reward, memory, and social bonding [12] ; and increases their willingness to share emotions. [13]

Another study compared the effects of a 20-minute massage with those of 20 minutes of reading, finding that both increase oxytocin levels. [14]

“It’s clear that physical touch is one of the important stimulants of oxytocin, and any kind of a setting where you’re more relaxed is going to tend to be associated with higher oxytocin levels,” Dr. Anawalt said.

For Valentine’s Day purposes, a 20-minute massage with scented oil to release oxytocin might be the perfect romance enhancer, he advised.


Miriam E. Tucker
February 13, 2014

professional counseling and care for the mind, body and spirit

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