It is theorized that in some CFS patients, the body’s ability to regulate the production of hormones by the endocrine system may be disrupted. When the body responds to physical or psychological stressors, the endocrine, or hormone, system reacts. A chain reaction is started by an area at the base of the brain called the hypothalamus. It releases a brain chemical called corticotropin releasing hormone (CRH), which causes the pituitary gland to release adrenocorticotropin hormone (ACTH). And finally, ACTH causes the adrenal gland to produce cortisol.
Research findings on the endocrine system from the NIH reveal two hormonal deficiencies in CFS patients: There is a CRH deficiency, and this deficiency affects the hormonal pathway, resulting in cortisol deficiency as well. These findings are very interesting because they offer a possible explanation for some of the symptoms of CFS. For example, low levels of either CRH or cortisol could cause insufficient stimulation of certain parts of the brain, resulting in fatigue, lethargy, and increased need for sleep – all hallmarks of CFS.
(Source: Chronic Fatigue Syndrome: A complete guide to symptoms, treatments, and solving the practical problems of CFS. By Gregg Charles Fisher, with contributions by Paul Cheney, M.D., Ph.D., Nelson Gantz, M.D., David Klonoff, M.D., and James Oleske, M.D.)