What to Ask Before Your Next Thyroid Test

Questions for Your Doctor Series

In 2017, the TRUST trial was published in the New England Journal of Medicine. Stott and colleagues randomised 737 adults aged 65 and older with subclinical hypothyroidism to either levothyroxine or placebo, with matched dose titration. After one year, the patients on the active medication showed no improvement in hypothyroid symptoms, no improvement in tiredness, and no improvement in quality of life compared to those on placebo. Their TSH normalised. The patients themselves felt no better. A 5-year follow-up published by Rodondi and colleagues in JAMA Internal Medicine in 2023 confirmed the original finding.

Subclinical hypothyroidism remains among the most common reasons for a new levothyroxine prescription. Patients with mildly elevated TSH and no clear symptoms are routinely medicated, often for life, on the assumption that lowering the number is beneficial. The randomised evidence does not support it.

The deeper problem is the reference range itself. In November 2002, the American Association of Clinical Endocrinologists narrowed the recommended TSH range from 0.5–5.0 to 0.3–3.0 mIU/L, reclassifying large numbers of previously “normal” patients as hypothyroid overnight. Broda Barnes had spent four decades documenting that such ranges were calibrated to a population already containing large numbers of undiagnosed hypothyroid people. He treated thousands of patients whose lab results were inside the range and whose symptoms — fatigue, cold sensitivity, weight gain, depression, recurrent infections, menstrual disturbance — resolved on a therapeutic trial of thyroid therapy. Autopsy studies in Graz, Austria found significant undiagnosed thyroid dysfunction in a substantial portion of the population.

The conversation a patient has with their doctor when their TSH comes back slightly elevated has not caught up with any of this. Most are told their result, told they have “subclinical hypothyroidism,” and offered the prescription. What they are not told is that TSH measures a pituitary signal rather than thyroid hormone activity in tissue, that a full panel including free T3, free T4, reverse T3, and antibodies tells a different story for not much more, that levothyroxine at TSH-suppressive doses is associated with bone density loss and atrial fibrillation, or that iodine depletion, halide displacement, mercury burden, and chronic stress are documented upstream causes of an abnormal result.

The document is a 12-page formatted guide — ten questions with their Key Facts, two paragraphs of context behind each, a routing table to find the questions that match your situation, and a one-page Quick Reference to print and take to the appointment.

Here is Question 7, one of the ten:

Question 7: What does the evidence say about levothyroxine for mild or subclinical cases — specifically the TRUST trial?

Key Fact: The TRUST trial (2017, NEJM) randomised 737 older adults with subclinical hypothyroidism to levothyroxine or placebo. After one year, the medication produced no improvement in hypothyroid symptoms or tiredness compared to placebo. A 5-year follow-up published in JAMA Internal Medicine in 2023 confirmed the result.

The TRUST trial, published in the New England Journal of Medicine in 2017 by Stott and colleagues, addressed a question that should have been answered decades earlier: does levothyroxine actually help patients with subclinical hypothyroidism? The investigators randomised 737 adults aged 65 and older, all with persistent subclinical hypothyroidism (TSH between 4.6 and 19.9 mIU/L with free T4 in the normal range), to receive either levothyroxine or placebo with matched dose titration. After one year, the patients on the active medication showed no improvement in hypothyroid symptoms, no improvement in tiredness, and no improvement in quality of life compared to those on placebo. Their TSH normalised — the laboratory number moved into the desired range — but the patients themselves felt no better. The 5-year follow-up published by Rodondi and colleagues in JAMA Internal Medicine in 2023 confirmed the original finding.

One context paragraph above. A second, going deeper into the mechanism and the implications, sits inside the document along with the other nine questions.

The other nine cover what the TSH test measures and what it cannot, how the reference range was set and how it has changed, the case for a full thyroid panel over a TSH-only test, the upstream conditions that produce an abnormal result, the Graz autopsy evidence on missed cases, the basal body temperature method as a home assessment tool, the documented long-term effects of levothyroxine on bone and heart, and the dietary and lifestyle approaches that address the conditions in which the thyroid is working.

The evidence in this document is drawn from the Unbekoming hormonal series, which assembles work from Broda Barnes (Hypo-thyroidism: The Unsuspected Illness, the four-decade clinical record of thyroid misdiagnosis), Lawrence Galton (co-author and medical journalist), David Brownstein (Iodine: Why You Need It, Why You Can’t Live Without It), David Stott (lead investigator of the TRUST trial, NEJM 2017), and Nicolas Rodondi (lead investigator of the 5-year TRUST follow-up, JAMA Internal Medicine 2023), alongside the broader research on TSH reference-range revision and the long-term effects of thyroid hormone replacement.

If you or someone you know has an appointment coming up — yours or a family member’s, a first thyroid panel or a long-term levothyroxine renewal — print the Quick Reference page and take it with you.

If there is a screening test, a prescription, or a procedure where you needed the right questions before you walked into the room, put it in the comments. The next topics will come from what you need most.

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Thyroid Testing: Questions for Your Doctor is available for download below.