The HPA Axis Explained 

Did you know that your body contains an interactive and ever-dynamic neuroendocrine (i.e., involving both the nervous system and the endocrine system) unit that is composed of three hormone-secreting organs? It is called the HPA axis and it plays a key role in your body's response to stress. 

Broadly speaking, stress refers to the disruption of homeostatic balance and your body’s subsequent attempt to actively restore and maintain homeostasis. The HPA axis contributes greatly to this entire process. However, its duties expand far beyond the stress response and an imbalanced HPA axis can, therefore, have enormous adverse effects on our health and well-being. 

Read more: How to handle stress at work >> 

What is the HPA axis? 

The hypothalamic-pituitary-adrenal (HPA) axis refers to the physiological communication and response between three hormone-secreting organs. As the name already suggests, these are: 

  • the hypothalamus
  • the pituitary gland
  • and the adrenal glands 

All three regulate your body’s reaction to stress. They play upon each other in a domino type effect and are responsible for the hormone cascade that is set in motion when we experience a stressful event. 

Besides regulating the stress response, they also influence a number of other functions, such as sleep (source), energy storage and expenditure, mood and emotions, memory (source), blood pressure, immune response, addiction (source), digestion, and appetite, to name just a few. 

This explains why the potential symptoms of HPA axis dysfunction are so numerous as many aspects of our physiology are directly related to this axis. 

Read more: HPA axis dysfunction symptoms >> 

HPA axis homeostasis 

While the main focus is often on how the HPA axis regulates our stress response, it also deals with several non-stressful stimuli such as sleep, appetite, and even light, and it is actually one of our body’s major control systems. 

Furthermore, as the HPA axis regulates sleep in multiple ways and vice versa, some even suggest that it should be called our energy regulator, rather than our stress regulator. 

Why is maintaining homeostasis of the HPA axis important? 

When we experience a stressful event, two response systems are activated, namely the sympathetic-adrenal-medullary (SAM) and the HPA axis. Each system releases a different type of panic hormones. While the SAM produces epinephrine and norepinephrine (or adrenaline and noradrenaline), the HPA axis produces corticoids, of which cortisol is the most well known. 

These freak-out compounds will then be released for several hours, even if and when the original stressor has long vanished. 

Luckily, the primary role of the HPA axis is to maintain physiological balance. So once a certain concentration of cortisol is detected in the bloodstream, it begins to return the body to homeostasis by ending or lowering its cortisol production. However, during this time, stress hormones continue to linger in the blood for a couple more hours until they are finally completely broken down by enzymes. 

This is why maintaining the equilibrium of the HPA axis is highly important as repeated and sustained HPA axis activity renders the body more sensitive to new stressors and can lead to burnout. 

Unfortunately, in today’s society, stressors are often chronic or long-term. This greatly affects your body's resistance, making you more susceptible to illness or disease. 

Read more: The General Adaptation Syndrome (3 stages of the stress response) >> 

How to restore HPA axis homeostasis? 

As mentioned above, the HPA axis and sleep interact with each other in multiple ways. This means that while a dysfunctional HPA axis and alterations in the rhythm of cortisol production are the cause of many cases of insomnia, chronic sleep disturbance can also negatively impact the HPA axis. 

This is why a good night’s sleep is one of the best ways to restore HPA axis homeostasis. 

Sound therapy, mindfulness, and yoga are some examples of great stress-relieving methods that also help you to relax and sleep. 

HPA axis and adrenal fatigue 

While reading this article, the term “adrenal fatigue” might have popped into your mind. It is a term that has been popularized quite a bit by the health and wellness media. It refers to the extreme fatigue that is caused by reduced cortisol levels after having experienced too much stress. A cortisol burnout, so to say. 

The cortisol switch supposedly remains on for too long, which eventually wears out the adrenal glands, resulting in extreme exhaustion due to a lack of cortisol. It certainly sounds plausible! But did you know that science does not support the notion that stress causes low cortisol levels? Furthermore, many people who believe they have adrenal fatigue often actually have completely normal cortisol levels. And a 2016 study even showed that adrenal fatigue is just a medical myth! 

HPA axis dysfunction, however, is a real phenomenon that has not only been verified but is also associated with several diseases. It refers to a gradual change in our stress response that happens after having been exposed to stressors for an extended period of time. This is why taking the time to reduce our stress levels on a daily basis is so important. Our adrenal glands will not malfunction from one day to the next, but stress does accumulate. And when we fail to take care of ourselves in time, the effects can be drastic. 

Takeaway 

The HPA axis refers to the physiological communication and response between the hypothalamus, the pituitary gland, and the adrenal glands. These three organs play an important role in your body’s reaction to stress and influence several other important physiological functions. 

Repeated and sustained HPA axis activity renders the body more sensitive to new stressors, which is why maintaining equilibrium is critical. 

Sound therapy, mindfulness, and yoga are some examples of great stress-relieving methods that also help you to relax and sleep. 

Would you like to stimulate recovery from chronic stress and restore homeostasis to your HPA axis? Then take a look at the Sonic Relaxation Mini-Course, where you will learn how to release stress by relaxing the body and quieting the mind. You too deserve a balanced HPA axis! 

If you are interested in learning how to identify the symptoms of HPA axis dysfunction in yourself, then check out this article where I discuss this topic in more detail. 

Article by Eline Stone

Listen to Sonic Yogi sound therapy here, or on your favorite streaming service.

Sources: 

https://www.mind-body-health.net/hpa-axis.shtml 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3860380/ 

https://academic.oup.com/jcem/article/90/5/3106/2837129 

https://pubmed.ncbi.nlm.nih.gov/12787553/ 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258225/ 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3782172/#:~:text=Early%20stressful%20life%20events%20and,traumata%20and%20posttraumatic%20stress%20disorder. 

https://www.scielo.br/pdf/pn/v3n1/v3n1a02 

https://www.mind-body-health.net/hpa-axis.shtml 

https://www.endocrineweb.com/endocrinology/overview-adrenal-glands 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4997656/

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