Bone, not adrenaline, drives fight or flight response
The "adrenaline rush" response to danger is little more than a medical myth, new research suggests.
A series of studies found that the raised heartbeat, quickened breathing and temporarily increased physical strength involved in the "fight-or-flight" response is actually triggered by a little-known hormone produced by the bones.
Tests in humans and animals identified osteocalcin as responsible for the acute stress response that helps us get out of danger, rather than adrenaline.
Published in the journal 'Cell Metabolism', the findings overturn decades of established thought on the role of adrenaline. They also suggest that the skeleton has a far broader evolutionary role in keeping us safe.
Prof Gerard Karsenty, of Columbia University, said: "The notion that bone mediates the stress response is totally novel, as is the notion that the adrenal glands do not mediate the stress response. This verifies the concept that bone was invented in part as a tool to fight acute danger.
"If you think of bone as something that evolved to protect the organism from danger - the skull protects the brain from trauma and the skeleton allows vertebrates to escape predators - the hormonal functions of osteocalcin begin to make sense."
One study examined by the Columbia team, which used mice, showed that spikes of osteocalcin were accompanied by the increased heart rate, body temperature and glucose usually associated with adrenaline.
Further tests revealed that mice incapable of producing adrenaline still showed fight-or-flight characteristics.
The study helps explain why younger humans, with healthier bones, have a more acute stress response.
The researchers now plan to extend their research to primates.
© Daily Telegraph, London