If TSH is the only test, that is not nearly adequate. TSH is a pituitary hormone that is affected by many variables, including the time of day when blood is drawn. You need to be tested for the actual, biologically active thyroid hormones, FT3 and FT4 (note that these are not total T3 and total T4 tests). In my opinion the best way to treat a thyroid patient is to test and adjust FT3 and FT4 levels with meds, as required to alleviate symptoms. Symptoms are what's most important.
once i went on synthroid, my thyroid levels went from 4.8 to 2.6 - that's all i know.
also, i've been extremely thirsty.
Please post the actual test results and reference ranges so that members can provide the best response.