I was hitting a low point where I could barely do much physical activity at all: digging a bucket sized hole in the yard and putting a plant in left me achy and exhausted for the rest of the day. was always couchbound and depressed in the evenings after work. I started seeing a new practitioner who looked at my thyroid labs, and he said that while my TSH / T3 / T4 were all "in range" on a standard test - but that my thyroid appeared stressed when he considered functional ranges. He prescribed a Iodine Loading Test from Hakala Labs /w Bromine, Chlorine & Flouride. My test results came back as iodine deficient (81% excretion - should be more than 90%) and very bromine toxic (18% excreted - should be less than 5%). I took 1.5mg Iodine a day and I was suddenly able to do light-to-moderate yard work. Now I am up to 3mg iodine per day and I am cheerfully going on walks in the evening after work, attending social events, and even yoga classes! In addition I take 300mcg of selenium, Thyrotrophin PMG glandular, and Celtic Sea Salt to help excrete bromine. He says that, starting low and going slow, we may eventually go up to 12.5mg iodine... and maybe even up to 50mg. I am feeling MUCH better, even at the start of this therapy. My energy is higher and my PEM symptoms are way down. Tenatively, it seems like I can reduce or even stop taking the d-ribose and L-carnitine i depended on, and feel pretty much OK. Some of what I thought was "mitochondrial damage" or ATP production blockage may have actually been subclinical low thyroid due to iodine deficiency, setting my energy metabolism into very low gear.