'Normal' Range Thyroid Levels Might Not Be Optimal for You

Patient Expert
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Conventional diagnosis and management of thyroid disease often focuses on being “in the normal range.” This refers to a key thyroid test — the thyroid stimulating hormone (TSH) test — falling within the test’s reference range. Many practitioners and official practice guidelines consider a “normal” TSH to indicate that you have normal thyroid function. The belief is that if you are within the normal range, your thyroid is normal, and you should be free of symptoms, whether you are seeking a diagnosis, or are already being treated for a thyroid condition.

But the TSH test may present several challenges to some patients.

First, conventional doctors don’t agree on the actual normal range. While many laboratories have a range of approximately .4 to 4.0 milliunits per liter (mU/L), there are doctors who believe that levels above 3.0 mU/L can cause symptoms, and suggest early-stage thyroid disease. These doctors believe that treating these patients may not only resolve symptoms, but prevent progression to overt thyroid disease.

Second, a subset of doctors believe that within the reference range, we all have an optimal set point, a level where our thyroid functions best, and where we have the fewest symptoms. So even if your level is within the normal range, you may show clinical signs and feel symptoms of hypothyroidism (an underactive thyroid) or hyperthyroidism (an overactive thyroid.) That subset of doctors considers not only the test results, but your symptoms, in deciding to treat you or in adjusting your dosage of thyroid medication.

Third, the TSH test measures a pituitary hormone, and is considered a marker and measure of thyroid function. The fact is, however, TSH does not measure the two primary circulating thyroid hormones: thyroxine (T4), and triiodothyronine (T3). Some practitioners believe that TSH testing is not enough, and diagnosis and treatment of thyroid disease should include tests to measure the free, unbound, and available levels of T4 and T3, known as the free T4 and free T3 tests. If these levels are low-normal, or below the reference range — even if the TSH is normal — these doctors will consider treatment for hypothyroidism. Similarly, if these levels are high-normal or above the reference range, even with a normal TSH, these doctors will consider treatment for hyperthyroidism.

Fourth, there is the issue of autoimmunity. Most thyroid disease in the United States is caused by two autoimmune diseases: Hashimoto’s thyroiditis and Graves’ disease. These autoimmune diseases can usually be detected by blood tests that check for thyroid peroxidase (TPO) antibodies for Hashimoto’s, or thyroid stimulating immunoglobulins (TSI) for Graves’ disease. TSH, free T4, and free T3 can all fall within the normal range, and yet if these antibodies are elevated, they indicate that you have an underlying autoimmune thyroid disease, along with the accompanying thyroid symptoms. In this case, there is evidence that early treatment may keep antibody levels from increasing and resolve your thyroid symptoms.

Finally, there is the controversy over “optimal” thyroid levels, versus simply being within the normal range. The conventional approach is based on the objective of getting a patient to any point within the normal range.

Some practitioners — more often those who practice from an integrative or more holistic perspective — believe that it’s not enough to be within the normal range. Patients should be at a level that is “optimal,” and safely resolving as many symptoms as possible. Your optimal levels may depend on your weight, whether you are pregnant or trying to conceive, your ability to absorb medication, and even whether you are an athlete or engage in intense exercise.

Ultimately, your optimal TSH, free T4, and free T3 levels are unique to you. But generally, many practitioners and patients have found that patients often feel their best when TSH levels are below 2.0, and the free T4 and free T3 levels are in the upper half of the reference range.

Guidelines for patients

  1. When you are seeking a diagnosis, or managing your thyroid treatment, be sure to find out from your doctor what he or she considers to be the key goal of your thyroid treatment. Is the doctor focused solely on getting your TSH into the normal range, or aiming for safe and optimal relief of your symptoms?
  1. If your doctor only uses the TSH test, encourage her to add free T4 and free T3. If your doctor refuses, it may be time to change practitioners and work with a practitioner who has a more comprehensive view of thyroid diagnosis and treatment.

  2. Always review your blood test results yourself. It’s never enough to get a call or report from the doctor or medical office that says “your thyroid is normal.” Ask for a copy of your test results, and be sure it includes the reference ranges for those tests at your laboratory so that you are fully informed.

  3. Keep track of how you feel at different levels and different dosages. If you had energy and relief of symptoms on a particular medication at a particular dosage at some point in the past, this gives you important data that you and your doctor can use to ensure you are getting optimal treatment going forward.

See more helpful articles:

What Thyroid Tests Should I Request?

How is Hypothyroidism Treated?

Hypothyroidism vs Hyperthyroidism: Understanding Your Blood Tests