Men and women have long argued about if getting kicked in the genitals or giving birth is more painful.
While the verdict may still be out, researchers are one step closer to finding the answer after uncovering why a person’s sex determines their pain threshold.
Scientists from the University of Arizona (UA) identified functional sex differences in nociceptors, the specialized nerve cells that produce pain, which suggested men and women experience pain differently.
For example, nociceptors in females were found to be more sensitive to a hormone linked to pain, while the nerve cells in men were not phased.
Their findings could pave the way for future advancements in painkillers like Ibuprofen that would treat men and women individually.
Men and women have long argued if getting kicked in the genitals or giving birth is more painful. While the verdict is still out, researchers are one step closer to finding the answer after identifying why a person’s sex determines their pain threshold
‘Until now, the assumption has been that the driving mechanisms that produce pain are the same in men and women,’ said Dr Frank Porreca, the research director of the Comprehensive Center for Pain & Addiction and professor at UA.
‘Conceptually, this paper is a big advance in our understanding of how pain may be produced in males and females,’ he added.
Nociceptors are activated when a person is injured, triggering a reaction that causes humans to remove themselves from the source of danger – like placing your hand on a stovetop or experiencing the jarring sting from a jellyfish.
The UA team tested how the nociceptor cells reacted to substances found in both men and women – prolactin, a hormone that causes lactation and breast development, and orexin B, which regulates sleep.
Female nociceptors were activated when given high doses of the hormone, while men’s showed no impact.
On the other hand, orexin B made male nociceptors more sensitive but did not affect female nociceptors.
The team then tried to block prolactin and orexin B.
Blocking prolactin stopped nociceptor activation in females but didn’t affect males – and obstructing orexin B worked the opposite way.
Dr Porreca, the study’s lead author, told DailyMail.com that the study ‘does not show that pain is worse in men or women but rather that the nociceptors in men and women are different.’
The researchers chose the two substances after reviewing a separate study that reported prolactin and orexin B sensitize nociceptors.
The researchers hope their findings can lead to better pain condition treatments that can be tailored to a person’s sex rather than a one-size-fits-all solution.
‘Different mechanisms of activation of the nociceptors means that we can find better ways to prevent their activation specifically in women or specifically in men to produce optimal treatment of pain in either men or women,’ Dr Porreca told DailyMail.com.
Current pain and anti-inflammatory medications like Ibuprofen work by normalizing the threshold for the nociceptors to be activated, but it does not address both men and women equally.
The team at the University of Arizona discovered there are different nociceptors for men and women that cause them to feel pain differently
Now that scientists know there are male and female nociceptors, it means medication could be produced that specifically caters to reducing orexin B and prolactin.
Speaking about their findings, Dr Porreca said: ‘This provides an opportunity to treat pain specifically and potentially better in men or women, and that’s what we’re trying to do.’
The US Food and Drug Administration’s existing approval of orexin receptor antagonists which treat sleep disorders would make it easier to prevent nociceptor sensitization.
‘We are bringing the concept of precision medicine – taking a patient’s genetics into account to design a therapy – to the treatment of pain,’ Dr Porreca said.
‘The most basic genetic difference is, is the patient male or female? Maybe that should be the first consideration when it comes to treating pain.’
As it turns out, pain thresholds are ‘not very different between men and women,’ Porreca said, but the thresholds might be activated for different injuries in men versus women.
The researchers findings could mean there will ultimately be a solution to the pain men experience from being kicked in the groin and the aftereffects of childbirth: sex-specific pain medication.
