I don't see that as definitive proof of anything, to be honest. I had shocking chest pain as a result of severe iron deficiency anaemia. This page from the NHS doesn't mention chest pain as a possible symptom of iron deficiency anaemia. https://www.nhs.uk/conditions/iron-deficiency-anaemia/ But this page from drugs.com (a US site) does : https://www.drugs.com/mcd/iron-deficiency-anemia ... Another condition in which lots of symptoms get ignored by the NHS is hypothyroidism. The NHS produced the following link to show the symptoms they consider as ones to be found in hypothyroidism : https://www.nhs.uk/conditions/underactive-thyroid-hypothyroidism/symptoms/ And yet a list produced by a patient charity for thyroid disease shows a much longer list : https://thyroiduk.org/if-you-are-undiagnosed/hypothyroid-signs-and-symptoms/ One of the major symptoms of hypothyroidism is fatigue which can be so severe that it hurts - a lot. ... And surely the same sort of comments can be made about ME. If a doctor was to create a list of symptoms they would expect to find in ME, it would be an awful lot shorter than a list created by patients. ... An n=1 anecdote. A few years ago I did a 4-part cortisol saliva test which showed that my cortisol was way over the range for most of the day. I was in a lot of pain, but I was also untreated for hypothyroidism and was iron deficient, so I can't prove that the high cortisol was adding to my overall pain, but I believe it was. For a few years after I discovered the high cortisol I took a supplement (an adaptogen) that lowers cortisol. It helped my pain levels rather a lot. I can't do saliva tests for cortisol any more though, because I have such low saliva that I can't spit, so I don't actually know what the result of my own self-help was.