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Everything you need to know about the HPA Axis: Part 1

I know the term ‘HPA Axis’ might not sound overly exciting. In fact, some might say it sounds a bit dull or boring! However, it’s one of my favourite topics, and I believe it’s such an underappreciated system of the body which doesn’t get enough recognition by the health care industry.

My own journey to wellness led me down numerous paths. I tried anything and everything to heal myself: naturopathy, homeopathy, Traditional Chinese Medicine, iridology, acupuncture, counselling, various diets, and more. Although these treatments all had a positive impact in one way or another, it wasn’t until I started understanding the HPA Axis (which led me to make certain changes to my lifestyle, diet and mindset) that I began to see drastic improvements in my health.

As a result, the HPA Axis has become my favourite system in the body because as I learnt more about it, I began to see that it influences virtually all aspects of our physical and mental health! For example, this system affects our energy levels, sleep patterns, hormonal balance, weight, digestion, appetite, skin, immunity, inflammation, mood, ability to cope with stress, as well as our blood sugar levels, cholesterol, blood pressure and temperature regulation.

I truly believe that the majority of our symptoms, particularly those that are vague or seemingly unrelated health symptoms (you know, the ones where you go to the doctor because you know within yourself that it’s not quite right, then they run a bunch of tests but everything comes back “fine” or “normal”) can be linked back to a dysfunctional or overworked HPA Axis. But, before we explore what that is and how to fix it, we first need to understand what the HPA Axis is, how it works and what its role is in our body.

What does ‘HPA Axis’ mean?

HPA Axis is short for the ‘Hypothalamic-Pituitary-Adrenal’ Axis, which refers to the interaction between three glands found in our body: the hypothalamus (H), pituitary gland (P), and adrenal glands (A).

As shown in the image below, these glands communicate in a hierarchy (which we’ll explore in detail later on):

What does the HPA Axis do?

The HPA Axis has two primary roles: 1. Maintaining basal homeostasis (which is just a fancy way of saying the body’s ability to maintain a stable internal environment despite changes in external conditions).

2. Initiating and regulating the body’s stress response system, which is often referred to as 'fight or flight mode'.

How does the HPA Axis work?

The hypothalamus, pituitary gland and adrenal glands work closely together in a cascade-like fashion, meaning that when one is released it will have either a positive (turning on) or negative (turning off) effect on other hormones, which allows the body to return to homeostasis.

I like to relate it to Fire and Rescue Services (weird analogy, I know, but stick with me!):

  • First, you have the person who identified the fire and made the call to emergency services. Similarly, the amygdala—one of the more primitive parts of the brain—is constantly scanning our environment for any threats or signs of danger, with the goal of protecting us and keeping us safe. If a threat is detected, the amygdala sounds the alarm by sending a message to the hypothalamus.

  • Next, you have the Emergency Service Operator who takes details of a situation and sounds the alarm at the firehouse. In our body, the Emergency Service Operator in this scenario is the hypothalamus which, when a threat is detected, sends a message to the pituitary gland to take action and prepare the body to deal with the threat. This communication occurs in the form of a hormone called 'Corticotropin Releasing Hormone' (CRH).

  • Every firehouse has a chief who's responsible for the efficient operation of the fire department and has control of all of its personnel and activities. Once the chief hears the alarm, it's their job to decide what actions need to be carried out by the department. For example, sending out the firefighters. Similarly, the pituitary gland is responsible for controlling the secretion of most hormones within the body depending on the information it receives from the hypothalamus. One of these hormones is called 'Adrenocorticotropic hormone' (ACTH), and it travels to the adrenal glands with one message: prepare the body to fight or flee from the threat.

  • Lastly, a firehouse is not complete without firefighters, who are responsible for putting out the fire. Once the fire is put out, they return back to the firehouse. In our body, the firefighters are the adrenal glands, and they release several hormones, namely cortisol, adrenaline and noradrenaline, to prepare our body to fight or flee. This is achieved by increasing our heart rate, and blood pressure, redistributing blood to our muscles and brain, releasing glucose (sugar) into our bloodstream to use as fuel, and turning off any function it deems as being non-essential for fleeing or fighting, such as those related to reproduction, digestion and immunity. Once the threat is eliminated, these hormones stop being released and the body returns to its normal relaxed state (homeostasis).

What happens when the HPA Axis gets activated too frequently?

The HPA Axis was designed to help us survive acute or short-term stress, such as running from a tiger. However, if the amygdala is constantly detecting threats (aka stressors), our HPA Axis is repeatedly activated which keeps the fight or flight response switched on. Over time, this takes a toll on the body, because the hormones released from the adrenal glands which prepare the body to fight or flee from danger impacts all bodily systems. For example:

  • The cardiovascular system, contributing to high blood pressure and high cholesterol.

  • The nervous system, leading to exhaustion, anxiety, low mood, headaches and insomnia.

  • The digestive system, making you more susceptible to food intolerances and symptoms of irritable bowel syndrome.

  • The immune system, reducing your ability to fight infections, colds and the flu, and may contribute to autoimmunity.

  • The reproductive system, leading to hormonal imbalances that may result in blood sugar disorders (e.g. insulin-resistance, diabetes), irregular menstruation, infertility or weight changes.

This is known as 'HPA Axis Dysfunction', which we'll be exploring in Everything you need to know about the HPA Axis: Part 2.


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