When Endocrinologists Briefly Narrowed the TSH Reference Range

Blood test.
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In the Fall of 2002, a key professional society, the American Association of Clinical Endocrinologists (AACE), 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, and the AACE actively encouraged doctors to consider thyroid treatment for patients who tested outside the target TSH reference range of 0.3 to 3.0, a far narrower window. 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, Hossein Gharib, MD, FACE, and 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 in 2002 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.

"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," said Dr. Gharib. "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 most 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, we thought that the AACE had finally moved into the 21st century in terms of its awareness that the outdated TSH reference range needed revisiting. But back in time they've gone again, unable to acknowledge what patients and some enlightened practitioners have known for years about the reality of TSH levels.

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