Your adrenal gland, which is responsible for releasing the stress hormone, becomes weak or sputters out.
see the STRESS AND STRESS MANAGEMENT page.
When we experience something threatening or stressful, two things happen immediately. The first thing is what we call the "fight or flight" arousal response. The whole body is gearing up to move quickly to get out danger. And the second thing is that the body releases the stress hormone cortisol. The body gears up immediately in the face of stressful stimuli. It goes to our energy stores, and releases glucose and insulin so that our muscles have the energy to deal with the stress. http://thechart.blogs.cnn.com/2011/11/16/the-vicious-physiology-of-stress/see also: Cushing's syndrome, fight or flight, acid-base imbalance