Understanding the Role the HPA Axis Plays in How You Feel
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When you’re feeling fatigued, irritable and sleepless, what’s going on inside your body? Or what about joy, relaxation, calm? Believe it or not, the way you feel doesn’t just happen – there are a whole host of processes going on in your brain and body that contribute to that feeling of satisfaction after a run or those feelings of anxiety before a big presentation. And one of the main control centers that deals with those reactions is the HPA axis.


HPA stands for hypothalamus-pituitary-adrenal, and is so named as an “axis” because they work in tandem and reciprocally. Their signaling processes are inextricable, and the systems they affect are also interconnected, which is why mood, stress and energy levels often go hand-in-hand – until you intervene with something like coffee or energy drinks.


So, how is the HPA axis supposed to work? And what’s happening when you add a stimulant to the mix? Let’s discuss:


HPA Axis & the Human Stress Response

Perhaps the most well-known function of the HPA axis is stress response. This axis was vital to human evolution, as it’s required for stress adaptation. So, what happens when you perceive a stressor? Say you’ve run into an ex unexpectedly on the street. There’s no time to get away – they saw you:


  • The amygdala received the stimulus, interprets it and decides it’s danger. It sends a distress signal to the hypothalamus.
  • The hypothalamus is the control center for the following cascade of events by communicating with the sympathetic nervous system – the one that controls involuntary movements and processes. The hypothalamus relays the distress signal to the adrenal glands through the nervous system. 
  • The adrenal glands flood the bloodstream with epinephrine (adrenaline), which redirects all available resources (oxygen, glucose, energy, etc.) to the body’s vital systems and muscles. 
  • The heartbeat rises, alertness is at an all-time high – this is the end of the nearly-instantaneous physiological changes that give you that stomache-drop feeling. Your body’s telling you it’s a fight-flight-freeze situation.


Now, what happens when this stressor stays for more than this initial danger moment the amygdala signaled? Say your ex has the audacity to walk up to you and start a conversation, instead of just waving and going away. This is where the HPA axis takes over:


  • When the initial mega-dose of epinephrine starts to wane, the hypothalamus will try to keep the sympathetic nervous system in that heightened state. It releases corticotropin-releasing hormone to signal the pituitary gland to mobilize the adrenal system.
  • The pituitary gland produces adrenocorticotropic hormone to signal the amygdala to release cortisol.
  • The amygdala releases a steady supply of cortisol into the bloodstream.
  • Alertness levels, heightened focus, increased heart rate, etc. all remain until such a time as the stressor leaves.
  • Once the stressor is removed, the parasympathetic nervous system takes over to bring everything back down to a normal level of function.


Wondering what happens when this system tries to deal with chronic, long-term stress? Check out our article: Understanding the Dangers and Mechanisms of Chronic Stress.


How HPA Activity Affects Your Mood

Under normal circumstances, the CRH and cortisol signaling by the HPA axis plays a role in serotonin and dopamine regulation. But this relationship is also reciprocal. Low levels of serotonin and dopamine, associated with low mood, let cortisol run wild, further contributing to an irritable exhaustion. On the other hand, overactivity of the HPA axis can reduce serotoninergic and dopaminergic activity, contributing to feeling crappy.


HPA overactivity is associated with several major mood and affect disorders, and is a main treatment target in modern psychiatry. The key is often to support serotoninergic and dopaminergic activity, and support GABA activity in tandem. GABA is the body’s calm-down chemical, and is associated with feelings of physical and mental calm.


Why is HPA overactivity relevant to mood in general? Because everyone is stressed on a chronic level. What a time to be alive.


The HPA’s Role in Your Daily Energy Levels

In theory, cortisol isn’t the absolute wrecker that it has come to be in our modern lives. Cortisol is actually a key neurochemical in your daily energy levels; the HPA axis uses it to support our sleep/wake cycle by releasing the most in the mornings and gradually lowering them throughout the day. This supports alertness in the daytime hours and calmness at night.


You probably know where this is going. In reality, cortisol is messing our energy levels up. Unless you’re lucky enough to live alone in the woods, you’re likely stressed and tired on a chronic basis like the rest of us. That’s because the HPA axis feels like it can’t shut down, because your amygdala is saying there’s something there that’s distressing and won’t go away. 


The result? Too much cortisol all the time, which, among a host of other things, leads to sleep disturbances and an anxious fatigue. Everyone knows what it’s like to get up after a long night of tossing, turning and reliving that awful interaction with your ex, and getting through the day solely through mainlining coffee the whole time.


Does it work? Technically. Is it really solving anything? Temporarily, maybe.


Are Stimulants Sabotaging Your Body’s Energy Resources?

So now that we know how the HPA axis works, let’s touch on what happens when you interfere with those neurochemical processes in an unbalanced way. When you consume a bunch of caffeine, you’re affecting three main neurotransmitters: 


  • Adenosine: Caffeine blocks this neurotransmitter, preventing you from feeling tired.
  • Epinephrine/Norepinephrine: Caffeine increases levels of this neurotransmitter, resulting in increased energy, alertness and focus.
  • Cortisol: Caffeine increases cortisol levels, which floods your body with energy.


Here’s what we’re missing with caffeine’s abilities: we’ve ignored the dopamine and serotonin of it all. Yet we’ve almost overactivated the adrenal system. That’s why an energy drink or quad-shot latte gets you the temporary energy boost you need, but often at the price of feeling even more stressed and more irritable. And when the caffeine runs out, you crash, because what it does is unbalanced and a little extreme.


Effective, sustainable energy boosts that come with a calm, balanced mood need to be just that: balanced. Feeling great is about giving your body the resources it needs to function at its best so it’s able to modulate all those neurochemicals correctly in the first place. Energy shouldn’t come with a price.


MTE: Biohacking Your Body’s Natural Energy Production

Every part of our physical and mental health is interconnected – stress and sleep affect your mood, energy, immunity, focus. And those all-important neurochemicals are the signalers that set states of mind in motion. And when we’re feeling tired, mad and stressed, we reach for energy drinks and coffee, even though we know caffeine is really just covering up the problem. 


But there is a better alternative to energy drinks that can replace excessive caffeine and sugar with real support for those chemical processes driven by the HPA. MTE is a greens powder supplement comprised of 13 powerful adaptogens, nootropics and superfoods. Meant as a replacement for energy drinks and excessive caffeine, our formulation promotes good feelings, healthy energy, quality sleep, focus, and more. Free of artificial ingredients and other crappy additives, we rely on clean, scientifically-supported, plant-sourced compounds to hack your brain and body back into homeostasis. Because what good is an energy boost if you’re jittery, irritable and exhausted? Check out our Ingredients page for more on our formulation, and order your first bag of your new go-to natural energy drink.

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