When Endocrinologists Briefly Narrowed the TSH Reference Range

Blood test.
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You may think that the thyroid stimulating hormone (TSH) test—so basic to thyroid diagnosis and treatment—is carved in stone from a medical perspective. But this is not the case, and there is controversy between integrative and conventional practitioners regarding the appropriate TSH reference range. There is even disagreement among conventional experts regarding the TSH reference range.

The latest controversy dates back to the Fall of 2002, when the American Association of Clinical Endocrinologists (AACE), a key professional society in the thyroid field, announced that as far as the Thyroid Stimulating Hormone (TSH) test—the so-called "gold standard" test for thyroid diagnosis—what was normal the year before was no longer normal.


According to the AACE, doctors had typically been basing their thyroid diagnoses on the reference range for the TSH test. The typical normal reference range levels at most laboratories ran from around 0.5 to 5.0.

The guidelines issued in 2002 narrowed the range for acceptable thyroid function to a target TSH reference range of 0.3 to 3.0, The AACE actively encouraged doctors to consider thyroid treatment for patients who tested outside the new reference range. At the time, AACE believed that use of the new, narrower range would result in proper diagnosis for millions of undiagnosed and untreated Americans who suffered from mild thyroid disorders.

At a press conference announcing the new reference range recommendations, Hossein Gharib, MD, president of AACE at the time, said: "There are more people with minor thyroid abnormalities than previously perceived."

At the time, the AACE estimated that the new guidelines doubled the number of people with abnormal thyroid function, bringing the total to as many as 27 million, up from the 13 million thought to have the condition under the old guidelines.

These new estimates briefly made thyroid disease the most common endocrine disorder in North America, far outpacing diabetes.

AACE initially made the decision to narrow the range because of data suggesting that many people who had low-level thyroid problems—reflected by levels within the old reference range—could be improved with treatment.

A narrower TSH range gave doctors reason to more carefully consider those patients.

According to Dr. Gharib:

The prevalence of undiagnosed thyroid disease in the United States is shockingly high, particularly since it is a condition that is easy to diagnose and treat. The new TSH range from the AACE guidelines gives physicians the information they need to diagnose mild thyroid disease before it can lead to more serious effects on a patient's health - such as elevated cholesterol, heart disease, osteoporosis, infertility, and depression.

The Road to Nowhere

This announcement from AACE represented a long-overdue and much-needed improvement in the level of awareness of endocrinologists. After decades of denying that patients within the normal range of TSH could in fact have a thyroid condition, they were acknowledging what patients and advocates had been saying quite vocally for years: that the high and low end of the normal range is not, in fact, normal for many people. 

Unfortunately, what was considered a very positive development for thyroid patients did not make a significant impact, for several reasons: 

  • Laboratories never adopted the new range as the formal reference range, meaning that only levels outside the older, broader range were flagged as abnormal.
  • The medical establishment continued to disagree about this, and eventually, the groups abandoned the recommendation to broaden the range, and continued to advocate for the current reference range.

For a brief moment, it seemed like the AACE and the endocrinology community had finally moved into the 21st century. They were acknowledging that the outdated TSH reference range needed revisiting. But they've gone back in time again, and more than a decade later, remain incapable of acknowledging what thyroid patients and some enlightened practitioners have known for years about the reality of TSH levels.

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