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    Hello – Both are antibody tests, but TSI measures stimulating antibodies only, while TRAb picks up all antibodies, both stimulating and blocking.

    Can you go back and ask the doc for Free T4 and T3? The medical guidance from the American Thyroid Association notes that TSH can be unreliable as a benchmark early in the course of treatment. They don’t state this for sure – but I would *guess* this applies to going back on antithyroid meds for a second round!