Adaptogens and HPA Axis
The HPA axis describes the interaction between the hypothalamus, pituitary gland, and adrenal glands. The hypothalamus and pituitary gland are located just above the brainstem, while the adrenal glands are found on top of the kidneys.
The main function generally attributed to the HPA axis involves the body's reaction to stress. When something stressful happens to us, our initial response is mediated by the sympathetic nervous system. This response occurs almost immediately, and results in the secretion of epinephrine and norepinephrine, both of which work to enact changes that you would generally expect if you felt stressed and/or frightened, like increased heart rate and perspiration in humans.
Then the HPA axis is stimulated, the hypothalamus responds to increased norepinephrine levels and so begins the cascade of other hormones associated with the stress response like corticotropin-releasing hormone, adrenocorticotropic hormone and cortisol.
Proper functioning of the HPA axis is essential for dealing with stress, the issue is when it is stimulated too much in the way of chronic exposure to stressors.
Elevated stress hormones are often linked to suppressed immune function, diabetes, obesity and cardiovascular disease along with cognitive and memory impairment and mood instability leading to anxious behaviours. Interestingly, baseline activity of the HPA axis can be affected by early experiences, suggesting that early exposure to stressors or trauma may lead to an overactive HPA axis in later life.
Adaptogens are considered stress-vaccines. They activate mild activation of the stress system in order for it to cope with more severe stress. Adaptogens act as challengers.
We can very loosely use the phrase, if you don't use it, you lose it. Adaptogens mildly use the stress-response, so you don't "lose it!"
But this is in fact only one way in which adaptogens help the body and mind adapt.