Low levels of cortisol indicates impaired functioning of adrenal or pituitary glands.
Certain infections,head injury,cancer, and some autoimmune diseases can lead to adrenal or pituitary gland damages.
Low cortisol levels are found in diseases like chronic fatigue syndrome, post-traumatic stress disorder, fibromyalgia and atypical depression.
In most of the cases, the adrenal cells that produce cortisol and aldosterone, are destroyed by anti- bodies that own immune system has developed.
General weakness, severe fatigue, increased skin pigmentation, weight loss, hypotension, abdominal cramps with changed bowel movements, muscle cramps, craving for salt, are symptoms of low cortisol blood levels.
You may check some information about adrenal fatigue, or adrenal exhaustion.
This condition must be corrected.

Best wishes!
Marija