To test thyroid function, you need to have Free T4, Free T3, which are actual
thyroid hormones and the pituitary hormone called TSH, which stimulates the
thyroid to produce
thyroid hormones. Many doctors will try to test only TSH and think that's good enough - it's not, because it doesn't give the full picture.
To test for they autoimmune condition, Hashimoto's, you need antibody tests, Thyroid Peroxidase Antibodies (TPOab) and Thyroglobulin Antibodies (TgAb).