Q. I have had an ongoing argument with my family doctor about the correct dose of Synthroid. The endocrinologist who diagnosed my condition said my TSH should be in the normal range, but my family doctor is not concerned that this test is abnormally low (0.1 with a normal of .35 to 7.0). He just looks at the normal level for the T4.
I’ve heard that too much Synthroid could weaken bones. Doesn’t a low TSH mean the dose is too high? The doctors seem to be rather evasive on the specifics of my case.
A. Adjusting the dose of thyroid medicine can be tricky, and the accepted levels on some blood tests have changed in the past several years. Your endocrinologist is correct that thyroid stimulating hormone (TSH) is often a more accurate measure of thyroid function than T4 tests. When the TSH test is as low as yours, it could mean that thyroid hormone levels are high. Too much thyroid can weaken bones and increase the risk of osteoporosis, so your concern is justified.
We are sending you our Guide to Thyroid Hormones with more information on the tests and how to interpret them. Many drugs, including oral contraceptives, Premarin, lithium, Tegretol and Dilantin, can affect thyroid test results, especially T4. Make sure the person interpreting your lab work is aware of every drug you take.
You and your doctor may need to work together to find the right dose of thyroid hormone. That is one that allows you to feel well while your lab test results are within an acceptable range.