So then the next step would be to measure T4 and T3 directly and to test for
thyroid antibodies. As Red Star says, 90% of
thyroid problems are autoimmune disease. Note, not everyone with autoimmune thyroid disease tests positive on antibody tests. Only 60-70%.
Essentially, if TSH is elevated, one or more of T4 and T3 are low or low normal and the patient claims hypo symptoms, then a trail of hormone replacement to see if that alleviates symptoms is reasonable.