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The Seesaw Physiology of Adrenal Fatigue

The seesaw balance between rest-and-digest and fight-or-flight physiology is one of the most important concepts for Adrenal Fatigue sufferers to grasp.


Dr. Andrew Neville


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I often reference the “Seesaw” of physiology in appointments with my patients, or the seesaw balance between rest-and-digest and fight-or-flight. This is one of the most important concepts for Adrenal Fatigue sufferers to grasp.

How the seesaw works

Let’s say you’re walking down the street, you turn the corner, and a tiger lunges at you. Immediately, you will tip the seesaw in the direction of your fight or flight response. This tipping of the seesaw activates the organ systems that you would need to flee or fight using your stress response (brain/limbic, nerves/ANS, hormones/HPA adrenals) and suppresses everything else.

The same thing would happen if you were to stand up in front of a thousand people for the first time to give a speech. Your body would jump into fight or flight and tip your seesaw into stress physiology. Like a seesaw when one side is dominant, the other is suppressed.

So what needs to happen in our body’s physiology and biochemistry to improve our chances of survival when a tiger’s making his move? Our body needs to provide additional fuel to the major muscle groups so that we can move…fast! This fuel comes in the form of oxygen and glucose.

The Stress Response System

To get the oxygen, our body sends energy to our lungs to take in air more rapidly. We increase our glucose by stimulating the adrenal gland to tell the liver to release a stored form of glucose into the blood (AKA increasing metabolism). Then, we need our blood to pump at a faster rate and with more force to push all of this fuel into the major muscle groups that will enable us to run. Our heart rate and blood pressure increase rapidly. When you’re in fight or flight this way, you primarily activate three organ systems: your heart, lungs, and sugar metabolism.

All of these changes are a result of a combined effort of your stress response system: the brain/limbic system, the HPA axis/adrenals, and your ANS/ autonomic nervous system. In the short-term, this will save our lives by protecting us from what is a real or perceived threat.

But that’s not all. What our body also accomplishes in these quick seconds—with the enormous efficiency only possible after hundreds of millions of years of evolution—is the shutting down of any “superfluous” bodily functions that require energy.

Can you guess which systems? All of the “rest and digest” systems, on the opposite side of the seesaw, are immediately and completely shut down. These organ processes are suppressed to conserve energy for the fight.


Processes like digestion, fighting viruses, balancing your menstrual cycle, building sperm, ovulation, repairing tissue, building bones, etc., are all highly energy-dependent jobs that would sap energy from the fight or flight process if allowed to continue. For this reason, in a combined effort, the HPA axis and autonomic nervous system flip the “off” switch to these systems, like flipping a breaker in the electrical panel in a house. What an excellent design!

Rest-and-digest vs. fight-or-flight

The digestive system is suppressed primarily at the level of stomach acid and digestive enzyme production: when a tiger is snarling, digestion superfluous process that cannot be used for immediate fuel so is shut down. In the case of the digestive system, you’ll develop digestive complaints from poorly digesting food and dumping it into the small intestine, such as irritable bowel, heartburn, and indigestion.

Organs of reproduction—also useless during a tiger attack (or a public speaking engagement, for that matter)—are efficiently suppressed, in both men and women, at every possible level. Hormonal problems will develop such as PMS, menstrual irregularity, low libido, and even infertility.

The exact same process occurs in the thyroid gland: during fight or flight, the energy going to the thyroid is diminished. Suppress the thyroid, and everything slows down, leading to weight gain, depression, constipation, and more.

The immune system is a bit more complicated and will be explained in detail in another monograph; it is not completely suppressed, but the majority of immune function ceases. You will develop immune system complaints such as frequent illness and allergies.

Together, the combined effort of the HPA axis/adrenals and ANS/autonomic nervous system accomplish this shift in body physiology into “fight or flight” within seconds. This explains why, when we are nearly in an accident on the highway, we immediately feel our heart race, our breathing increase, and we begin to perspire. Our pupils dilate, and our muscles tense. Every cell in the body is affected by this shift into fight or flight.

We don’t have to think for a second about this protective reaction when faced with a threat. This incredibly efficient and life-saving fight or flight response is all normal and valuable to us since it has ensured our survival up to this point.

But what happens if you activate this system— even just a little bit— all the time?

The crux of the entire problem of Adrenal Dysfunction is that you are constantly accessing a system that was designed for short-term acute usage. What was once life-saving now becomes damaging and dangerous. If our fight or flight response is overtaxed (too often and for too long), the effects of being in a perpetual stress response lead to the deterioration in each one of our bodily systems.

The systems and organs that are constantly overstimulated—cardiovascular, respiratory, and your sugar metabolism—eventually weaken and lose their ability to adapt and function smoothly and effortlessly. For example, the damaged cardiovascular system leads to blood pressure issues and cardiovascular disease, and the damaged metabolism leads to metabolic syndrome and, eventually, diabetes.

At the same time, we are chronically suppressing our digestion, immunity, and reproductive hormones, as well as our thyroid. We will start to see symptoms from this suppression in these very systems, as noted above, and it will even affect growth and repair, leading to poor wound healing and osteoporosis.

I understand that this may seem a gloomy picture, but I there is something that can be done about it. This can all shift, heal,  and repair; it simply requires a holistic program that addresses the cause of the condition.


Dr. Andrew Neville


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