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The HPA axis, also known as the hypothalamic-pituitary-adrenal axis, is a crucial system in the human body that plays a significant role in regulating our response to stress. The HPA axis is a complex network of interactions between the hypothalamus, pituitary gland, and adrenal glands.
An organism‘s survival and evolutionary fitness requires a high sensitivity to its environment, “integrating cues of resource availability, ecological factors, and hazards within its habitat.” Researchers Dana N. Joseph and Shannon Whirledge explain, “events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic-pituitary-adrenal (HPA) axis” (2017).
Key Definition:
The HPA axis, also known as the hypothalamic-pituitary-adrenal axis, is a complex network of interactions between the hypothalamus, pituitary gland, and adrenal glands. It plays a significant role in regulating our response to stress.
The Stress Response
The “stress response coordinates endocrine, neural, cardiovascular, and immune systems with the aim to maximize survival chances” (Hofland, Bakker, Feelders, 2015). The HPA axis maximizes our body for survival behaviors through the release of a hormone commonly known as cortisol.
When we encounter a stressful situation, the hypothalamus in the brain releases corticotropin-releasing hormone (CRH). This hormone signals the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH then travels through the bloodstream to the adrenal glands, located on top of the kidneys. In response to ACTH, the adrenal glands release cortisol, commonly known as the stress hormone. Cortisol helps the body cope with stress by increasing blood sugar levels, suppressing the immune system, and mobilizing energy reserves.
After the release of cortisol levels into the blood, a balancing process occurs, allowing the body to return to normal functioning. Basically, once cortisol levels rise, it sends signals to the hypothalamus and pituitary gland to stop producing CRH and ACTH, the curtailing production of these hormones brings the body back to a homeostatic balance. When working properly, this feedback loop regulates the stress response and prevents chronic activation.
Behavioral and Emotional Response to Heightened Cortisol Levels
Daniel Goleman explains that “when we are under stress, the HPA axis roars into action, preparing the body for crisis. Among other biological maneuvers, the amygdale commandeers the prefrontal cortex, the brain’s executive center. This shift in control to the low road favors automatic habits, as the amygdale draws on knee jerk responses to save us. The thinking brain gets sidelined for the duration: the high road moves too slowly” (Goleman, 2007).
Basically, activation of the HPA axis signals to the body to prioritize survival activity. Other non-essential activities are temporarily suspended or curtailed until the body returns to a normal state.
The physical changes of the body signal that something is wrong. When the changes are significant enough, they puncture through the veil of consciousness (somatic awareness), and we register the physical change as an emotion (See two factor theory of emotion). Lawrence Heller, trauma specialist, wrote that “massive fluctuations in the HPA axis…are often accompanied by strong emotions: rage, disgust, terror or joy and the feeling that all is well” (Heller & LaPierre, 2012).
Prolonged Stress
However, prolonged or chronic stress can disrupt this axis, leading to dysregulation in the cortisol response. This can result in various health issues, including adrenal fatigue, sleep disturbances, hormonal imbalances, and weakened immune function. Gabor Maté MD explains that “the temporary elevation of cortisol that occurs in episodes of acute stress is healthy and necessary.” However, he emphatically continues, “not healthy are the chronically elevated cortisol levels in chronically stressed persons” (2008). The continuous heightened cortisol levels in the blood begin damage organs, interfering with healthy functioning in the body.
HPA Axis Sensitivity
Daniel Siegel reports that adverse childhood experiences impact normal functioning of the HPA axis (Siegel, 2020). The malfunctioning HPA axis may become hypersensitive to external and internal stimuli. In Scott Strossel’s comprehensive book on anxiety, he explains that “if you have a hypersensitive HPA axis, you’re much more likely to develop PTSD or some other anxiety disorder in the aftermath of a traumatic experience; if you have a low-reactive HPA axis, you will be much more resistant, if not largely immune, to developing PTSD” (2015).
Plenty of research supports Strossel’s hypothesis. One research paper wrote, “the effect of childhood trauma on the development of psychopathology in adulthood is attributable to the HPA axis, which when activated during the developmental process would be permanently unstable, hyper-stimulated, vulnerable, or dysfunctional” (Tofoli, ettt al., 2011). Early life stressors play a preeminent role especially in later development of mood and anxiety disorders.
Research with rats discovered that attentive parenting had a lifelong impact on the young pups. “Pups whose mothers had licked and groomed them grew up to be laid-back in response to stressful experiences, curious, eager to explore new surroundings, and resilient in the face of stress. But baby rats whose mothers rarely licked and groomed them grew up to be fearful and stressed out, hypersensitive to being startled and prone to freezing in fright at anything unfamiliar or unexpected” (Davidson, 2012).
Keeping The HPA Axis Functioning Properly
To keep the HPA axis functioning optimally, it is essential to adopt stress management techniques such as exercise (Southwick & Charney, 2018), meditation, adequate sleep, and maintaining a balanced lifestyle. Mental health often falls back to the basics. Typically, we should always begin there.
Maté explains that “psychological factors such as uncertainty, conflict, lack of control, and lack of information are considered the most stressful stimuli and strongly activate the HPA axis. Sense of control and consummatory behaviour result in immediate suppression of HPA activity.” Maté continues, “lack of essential information about ourselves and our situation is one of the major sources of stress and one of the potent activators of the hypothalamic-pituitary-adrenal (HPA) stress response.” Accordingly, he adds, “stress wanes as independent, autonomous control increases” (2008).
By nurturing our HPA axis, we can promote overall well-being and resilience in the face of life’s challenges. Understanding the intricate workings of the HPA axis provides valuable insights into the body’s response to stress and offers opportunities to develop effective strategies for managing and mitigating its impact.
References:
Davidson, Richard (2012). The Emotional Life of Your Brain: How Its Unique Patterns Affect the Way You Think, Feel, and Live–and How You Ca n Change Them. Avery; 1st edition.
Heller, Lawrence; LaPierre, Aline (2012). Healing Developmental Trauma: How Early Trauma Affects Self-Regulation, Self-Image, and the Capacity for Relationship. North Atlantic Books; 1st edition.
Hofland, J., Bakker, J., & Feelders, R. (2015). What’s new on the HPA axis?. Intensive Care Medicine, 41(8), 1477-1479. DOI: 10.1007/s00134-015-3771-8
Goleman, Daniel (2007). Social Intelligence: The New Science of Human Relationships. Bantam; NO-VALUE edition.
Joseph, Dana; Whirledge, Shannon (2017). Stress and the HPA Axis: Balancing Homeostasis and Fertility. International Journal of Molecular Sciences, 18(10). DOI: 10.3390/ijms18102224
Maté, Gabor (2008). When the Body Says No. Trade Paper Press; 1st edition.
Siegel, Daniel J. (2020). The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are. The Guilford Press; 3rd edition.
Southwick, S., Charney, D. (2018) Resilience: The Science of Mastering Life’s Greatest Challenges. Cambridge University Press; 2 edition.
Strossel, Scott (2015). My Age of Anxiety: Fear, Hope, Dread, and the Search for Peace of Mind. Vintage; Reprint edition.
Tofoli, S., Baes, C., Martins, C., & Juruena, M. (2011). Early life stress, HPA axis, and depression. Psychology & Neuroscience, 4(2), 229-234. DOI: 10.3922/j.psns.2011.2.008
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