What Do Female Hormones Have to Do with Pain & Pain Medications?

We've known for a long time that women and men experience pain differently and that women experience certain pain conditions like migraine disease more frequently than men. We also know some kinds of pain medication work better for women than for men.

But the whys and hows of these differences have until now been a complete mystery. Recently researchers at the State University of New York Downstate Medical Center have been able to make some headway in answering these important questions.

One of the big revelations of their research is that estrogen levels play a role in the way some opioid receptors react to opioid pain medications. Opioid receptors are molecules found primarily in the brain, spinal cord and digestive tract that receive messages from chemicals with pain killing properties called opioids. The researchers found a difference in the amount of these receptors between men and women, indicating that estrogen and progesterone are essential for the formation of this specific type of opioid receptor. They also observed differences among women depending on where they are in their menstrual cycles. When women were at the peak of their estrogen and progesterone levels, the level of opioid receptors in their spinal cords were four times higher.

Researchers believe this information about the connection between female hormones and certain opioid receptors could explain why some drugs used to treat pain (such as pentazocine, nalbuphine and butorphanol) are more effective for women than men. They also suggest doctors take the stage of their patients' menstrual cycles into account when selecting pain medications for them because medications that may be very effective during one part of their cycles may be less so during other phases.

Interestingly, butorphanol is mostly prescribed for treatment of the pain-related aspects of migraine and childbirth. Perhaps this is because medicine has already made the realization it is less effective for pain among men even without the knowledge we now have from this new research.