Extreme stress can cause a temporary rise in blood glucose. This can be a result of, for example, trauma, surgery, heart attack or stroke. Drugs, including corticosteroids, tricyclic antidepressants, diuretics, epinephrine, estrogens (birth control pills and hormone replacement), lithium, phenytoin, and salicylates, can increase glucose levels, while drugs such as acetaminophen and anabolic steroids can decrease levels.
Dr. Baraniuk's Georgetown research team has found a number of abnormalities in the brains of Gulf War Syndrome patients with chronic fatigue syndrome. High lactate levels at rest, low lactate levels during exertion and nerve damage in fatigue and pain producing areas of the brain could result in low energy and cognitive problems - http://www.cortjohnson.org/blog/2013/07/01/your-brain-without-energy-broken-brain-energy-loop-wipes-out-cognitive-functioning-gws-me-cfs/