There is an assumption in the field that estrogen modifies oxytocin in a clear-cut manner, and that is it increases oxytocin across the board. That is not what I'm finding.

Anyone who has struggled to decide whether or not to take a hormonal replacement or supplement therapy knows that clear-cut advice is hard to come by. The body's endocrine system is so complex, convoluted and nuanced that, in many cases, definitive answers just aren't known yet. Assistant Professor of Psychology Jennie Stevenson is piecing together one part of the hormonal puzzle.

Stevenson studies the hormone oxytocin, which is well known for its role in birthing and breastfeeding. Oxytocin also appears to be involved in "pretty much everything under the sun," which has created a market for oxytocin supplements, Stevenson says, despite significant holes in our knowledge of what the hormone does and how it affects the body.

Stevenson conducts her research with prairie voles, one of the few rodent species without a regular estrous cycle. Instead, female prairie voles come into heat after being around a male for a couple of days. The absence of a cycle means Stevenson does not have to account for that variable in her research. Prairie voles also have some physiological similarities to humans in their ability to engage in social behaviors, which makes them a good model system for understanding human physiology.

Stevenson has studied how boosting levels of another well-known hormone, estrogen, modifies the way oxytocin responds to stressors. "There is an assumption in the field that estrogen modifies oxytocin in a clear-cut manner and that is it increases oxytocin across the board," she says. "That is not what I'm finding." Instead, Stevenson has found that estrogen changes when and how oxytocin is released after stress.

One tool Stevenson has used to better understand the interaction between estrogen and oxytocin is radio transmitters that record data from her animals' hearts. Prairie voles have a human-like system that regulates their hearts. The heart and mood are so closely linked that arrhythmias in the heartbeat can indicate anxiety or other psychological disorders.

Stevenson's research into the roles and workings of oxytocin point to how complicated the body is. "It's really complicated; especially, anything with estrogen is incredibly complicated," she says. "It's so confusing for the general public, and people are looking wherever they can to find information about what to do.

Posted Sept. 27, 2010