I had all the symptoms of CFS when I went off of my hypothyroid meds. Now that I'm back on, I'm fine. Thyroid is one of those things that doctors can miss, (or not treat properly) that can cause people problems.
And its also something that cannot be identified without a specific blood test (TSH). Meaning that all the alternative quackery practitioners will never find it. They'll do muscle testing instead. Might as well consult the Urim and Thummim.