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The TSH Normal Range: Why is There Still Controversy?

Insights from One of the Nation's Leading Endocrinologists, Dr. Jeffrey Garber


Updated June 02, 2014

Technician holding blood sample in clinical laboratory with test results
Rafe Swan/Cultura/Getty Images

There's no question that thyroid treatment is an area of controversy. Perhaps one of the most confusing issues for patients today is the issue of the changing "normal" reference range for the TSH -- thyroid stimulating hormone -- test, which is relied on by most conventional practitioners to detect and monitor thyroid problems.

In late 2002, the National Academy of Clinical Biochemistry (NACB) issued new guidelines for the diagnosis and monitoring of thyroid disease. In the guidelines, the NACB reported that the current TSH reference range -- which usually runs from approximately 0.5 to 5.5 -- may be too wide and actually may include people with thyroid disease. When more sensitive screening was done, which excluded people with thyroid disease, 95 percent of the population tested actually had a TSH level between 0.4 and 2.5. As a result, the NACB recommended reducing the reference range to that. Meaning, anything below or above that could be a sign of thyroid disease.

The NACB guidelines led to a recommendation in January 2003 by the American Association of Clinical Endocrinologists (AACE), calling for doctors to "consider treatment for patients who test outside the boundaries of a narrower margin based on a target TSH level of 0.3 to 3.0." The statement also said: "AACE believes the new range will result in proper diagnosis for millions of Americans who suffer from a mild thyroid disorder, but have gone untreated until now."

In research published in the Journal of the American Medical Association in 2003, Dr. Vahab Fatourechi and fellow resarchers estimated that if the range were narrowed according to the AACE recommendations, the total number of people with thyroid disease would expand from approximately 5 percent of the population to an estimated 20% of the population, with most of the added patient population falling in the hypothyroid/underactive category. This represents a dramatic increase in the number of thyroid patients nationwide, from an estimated 15 million, to a total of some 60 million Americans.

At the same time, however, a 2002 consensus conference made up of representatives from the key professional groups involved in thyroid treatment -- the American Association of Clinical Endocrinologists, the American Thyroid Association, and the Endocrine Society -- published their findings in 2004, recommending against routine treatment of patients with TSH levels of 4.5 to 10.0 mIU/L.

Many doctors, and the AACE itself, refer to the TSH test as the "gold standard" for measuring thyroid function. AACE recommendeds the new target range of 0.3 to 3.0. Yet, now, almost four years later, America's testing laboratories still use the old reference range of .05 to 5.5, and results are flagged by laboratories as abnormal only if they are outside the 0.5 to 5.5 reference range. And doctors remain divided. Among conventional physicians, some refuse to diagnose hypothyroidism unless the TSH test results are outside the traditional normal range, and flagged as abnormal by the laboratory. Other practitioners are following the recommendations of NACB and AACE, and are willing to diagnose hypothyroidism in patients with TSH levels above that range.

Given that TSH test is touted as the "gold standard" for diagnosis and management of thyroid conditions, and is relied upon -- even considered inviolable -- by legions of doctors, isn't it reasonable to expect that doctors would agree as to what the results of their gold standard test mean?

Recently, I had an opportunity to explore this question with Jeffrey Garber, MD, FACE, one of the nation's leading thyroid experts. Dr. Garber was speaking on behalf of the American Association of Clinical Endocrinologists (AACE), and serves AACE's Treasurer. Dr. Garber is Chief of Endocrinology at Harvard Vanguard Medical Associates, and is affiliated with both Beth Israel Deaconess Medical Center and Brigham and Women's Hospital, two Harvard teaching hospitals. Dr. Garber also serves as Assistant Clinical Professor at Harvard Medical School. He also serves on the American Thyroid Association's Lab Services Committee, and the Medical Advisory Counsel of the Thyroid Foundation of America. Dr. Garber is also author of the Harvard Medical School Guide to Overcoming Thyroid Problems.

I asked Dr. Garber why he feels there are such differences within the endocrinology community.

According to Dr. Garber, guidelines are not meant to function as a replacement for the judgment of a physician's individual practice. While in his published writings, Dr. Garber has said he doesn't feel that treating subclinical hypothyroidism is typically warranted, Dr. Garber said in practice, he doesn't hesitate to treat a patient who is in the 2.5 to 5.5 TSH range if he judges it to be potentially helpful.

According to Dr. Garber: "My view of what to do as an individual is different than what should be done for a population. I'm not the surgeon general; I don't take care of 300 million people."

For example, Dr. Garber cited the example of a patient in the higher end of the normal TSH range who is experiencing infertility or depression. Says Garber: "Even though hypothyroidism may not be fully responsible, what a mistake not to address a potentially reversible component."

Dr. Garber even feels there is a role for preventive treatment and monitoring. "If I see a 25-year-old woman with a TSH of 4 who is planning to get pregnant, it's reasonable medicine to say 'let's put you on something in advance or check your thyroid early in pregnancy,'" says Garber.


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