The adrenal glands, which sit on top of the kidneys are part of the endocrine system, and release hormones. The adrenals release hormones such as cortisol, testosterone, epinephrine, and norepinephrine. The adrenals are just one player in an entire system that controls our stress reactions in the body. This system is called the HPA Axis (Hypothyllamic-Pituitary-Adrenal). Many different types of stressors can activate the HPA axis. In healthy, normally functioning people, the HPA axis is activated when needed, and shut off when the stressor is resolved. The problem is that in today’s busy world, many of us hardly ever get a break from the HPA axis being switched to the "on" position.
The over-activation of the HPA axis over long periods of time can lead to higher production levels of Cortisol, our primary stress hormone. Longer term problems can lead to cortisol that is too low, and lead to Adrenal Fatigue.