Free t3 corolates best with hypothyroid symptoms and many people feel better when this is kept higher in the reference range, as t3 is the biologically active
hormone. You have to keep in mind that Synthroid is only t4 (storage
hormone) that must convert to the biologically active t3. If your body is not able to do this well enough (conversion process), then an addition of a t3 medication may be beneficial in helping to relieve some of your symptoms.