Hello @michele1947
As a veterinarian, I can tell you that in dogs other illnesses can affect thyroid levels. So they should be doing a total thyroid screen, not just looking at TSH. That is probably what your endocrinologist is doing for you. If your other levels of thyroid hormones are normal then you don't need more synthroid. TSH is Thyroid Stimulating Hormone and it tells your body to produce more thyroxine (T4), etc. If the TSH is elevated by other disease, then looking at the T4, T3, total T4, and other thyroid hormones tells you if you should increase Synthroid or not. You can ask your endocrinologist some questions to see what they are testing.