Although thyroid hormone supplementation suppresses endogenous thyroid hormone production via negative feed-back loops, their benefits may yet justify their use in the context of low thyroid hormone function. Positive results from early trials in ME/CFS and fibromyalgia—as well as anecdotal evidence described by ME/CFS practitioners and patients in numerous books—indicate that treatment for ME/CFS with thyroid hormone supplementation merits further investigation. The gene discussed is TG; the disease is fibromyalgia.