My hunches come from reading others symptoms who've been tested comparing that to my own. I have a main symptom of Wilson's disease (copper toxicity), dystonia, which is not really common although I don't think I have wilson's; just high copper. Dr. Lawrence Wilson's articles on this also have helped me out. Combined with copper I suspect some sort of hormonal imbalance.
Of course nothing can replace thorough testing.
EDIT: wanted to add, that the other way I knew was that whenever I ate or drank stimulants like sugar, chocolate and coffee especially... my neurological symptoms would actually immediately lessen. I concluded that it was a boost in ceruloplasmin production by the adrenals which were responding to the stimulants.