New research discovers that the fight or flight response is mediated by the skeletal structure. The fight or flight response has been previously categorized as a response from adrenaline, and we now know that the skeleton plays a role in releasing a hormone from the bones which triggers the cascade of fight or flight responses.
Columbia University researchers have discovered that at the first recognition of danger, the brain sends a message to the skeleton, and the skeleton releases a hormone called osteocalcin into the bloodstream. The most interesting part of this discovery is that osteocalcin is so important to the fight or flight response that bony vertebrate animals cannot even begin the process of the stress response without the hormone being released from the bones.
The bones release osteocalcin within 2-3 minutes after a source of danger is detected. As osteocalcin increases, so does heart rate, blood sugar levels, and temperature—the main indicators that a fight or flight response has been triggered. Scientists examined this phenomenon in both animals and humans. In genetically modified mice which were either rendered incapable of producing osteocalcin or were engineered to not have the osteocalcin receptor, they did not respond to the experimental stressor at all.
Scientists were also able to induce a fight or flight response by injecting the hormone directly into the test subjects, providing concrete evidence of the role which osteocalcin plays. This has now provided an answer to a question that has been asked by biologists: how do patients and animals who have no adrenal glands or adrenal hormones (leaving them unable to produce adrenaline in the fight or flight scenarios) develop their acute stress responses? The answer is in the ability of the body to trigger the response from the osteocalcin flooding the bloodstream.
This discovery has brought scientists back to the drawing board about what we know about acute stress responses. It’s also changing how we think about our bones and giving us one more reason to view our bones as the living structures that they are.
- Berger, Julian Meyer, et al. “Mediation of the Acute Stress Response by the Skeleton.” Cell Metabolism, vol. 30, no. 5, 5 Nov. 2019, pp. 890–902., doi:https://doi.org/10.1016/j.cmet.2019.08.012.