Research has shown numerous physical biomedical abnormalities in people with M.E. including:
Immune System: chronic immune activation and dysfunction, evidence of persistent viral infection, low natural killer cells
Brain / Central Nervous System: objective measurement of dysfunction deficits in working memory, concentration, information processing, white and grey matter abnormalities, abnormal neuro-genetic expression
Endocrine System: impaired activation of the hypothalmic-pituitary-adeenal (HPA) axis, abnormalities of neuroendocrine-genetic expression
Muscular: structural and biochemical abnormalities including impaired muscle recovery after exercise
Heart and Circulatory System: hypoperfusion, impaired vascular control, low blood volume
Others: gastrointestinal dysfunction including food intolerance, mitochondrial dysfunction including abnormal mitochondrial associated gene expression
A diagnosis of M.E. is not normally considered unless activity levels are reduced by at least 50%. As there is not yet a test for M.E., it is usually made on the presence of certain symptoms, along with tests to exclude other possibilities, many of which have similar symptoms to M.E. (e.g. glandular fever, M.S., some cancers, other neurological conditions).
It is thought by some doctors that one of the main, underlying problems in M.E. is "metabolic dysfunction" i.e. hypo-thyroidism and hypo-adrenalism, with treatment aiming to remedy these deficiencies. For further details see the "What other help is available?" section and "Your Thyroid and how to keep it healthy", as mentioned in "Further Reading".
The main diagnostic symptoms of M.E. are as follows:
1) Exhaustion and Post-Exertional Malaise - Exhaustion is a principal symptom of M.E., is experienced by all sufferers, and must not have previously been a problem. It is caused by trivially small exertion - physical or mental - compared to before the onset of the illness. Activity can put someone in bed for days or, if overdone, can cause a major relapse. It produces a post-exertional malaise, accompanied by muscle pain and weakness, that can begin soon after activity or be delayed by as much as 72 hours, which can make planning anything very difficult. The exhaustion in M.E. is severe, disabling, and totally unlike that experienced by healthy people. Some have described it as being totally drained of energy and "having their plug pulled out". Unlike normal tiredness it is not helped by exercise and would be made worse by it.