The TSH Normal Range: Why is There Still Controversy?

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

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 has been 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 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 those levels. 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 researchers 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 recommended the new target range of 0.3 to 3.0. Yet, the new target range was never officially adopted by laboratories, professional associations, HMOs, and insurers. More than a decade later, the AACE has backed down on their previous recommendations. 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, most continue to refuse to diagnose hypothyroidism unless the TSH test results are outside the traditional reference range and flagged as abnormal by the laboratory.  

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?

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.

But while Garber suggested that he felt that the proposed new guidelines recommendations would help more patients get properly diagnosed and treated, he was clear that these guidelines shouldn't automatically dictate treatment for anyone who falls outside the range. Said Garber: "The TSH normal range should not be a polarizing issue. But as often seen in medicine, it's easier to agree on the extremes. When you get closer to what's marginal, it's a harder call. We need to realize that it's a continuum. If people know that this particular group is more likely to have thyroid disease than the group that's lower, it doesn't commit you to treatment and doesn't say that it's not appropriate, it says to follow it, and maybe intervene."

The Implications for Patients?

After speaking with Dr. Garber, it was clear that endocrinologists would not reach consensus on the issue of the TSH normal range, and I was right. Nearly a decade later, the situation remains the same, with some doctors interpreting test results more liberally, and others relying solely on the reference ranges. 

So where does that leave patients?

Dr. Garber said that when it comes to making a decision to diagnose or manage patients who are in this questionable TSH range of 2.5 to 3.5, endocrinologists can be particularly helpful. Says Garber: "It's not unreasonable for someone on endocrine treatment, who is not optimally treated, to ask to see an endocrinologist." 

I mentioned that many patients face long waits for the limited numbers of endocrinologists available. For those patients, Dr. Garber said that there are efforts underway to get more endocrinologists into the pipeline. Says Garber: "We'll never be able to take care of all the people...but we're also looking at more thyroid education for physician extenders such as nurse practitioners and endocrine nurses."

 

My Thoughts

My experience, and the experience of my readers, tends to contradict Dr. Garber's vision of endocrinologists as being especially capable and willing to identify those in the high-normal TSH range who merit treatment. In the past, I have referred to endocrinologists, not entirely jokingly, as the "accountants of medicine," due to a tendency to overfocus on lab test reports to the exclusion of symptoms and clinical observation.

As thyroid patients, many of us have even adopted as our rallying cry, "We're patients...not lab values." But given that a GP or family practice doctor may not feel confident about diagnosing and treating borderline thyroid problems without fear of medical or legal repercussions, perhaps Dr. Garber is right that endocrinologists may be the next line of defense. At minimum, as specialists, they may feel their additional credentials give them license and authority to make those "close call" diagnoses that feel riskier to their colleagues in general practice.

Unfortunately, however, even with ramped up training programs for endocrinologists and what Dr. Garber referred to as "physician extenders," most of us are still limited to primary care, general practice and HMO doctors for thyroid diagnosis and treatment. And here, the lack of consensus standards, the need to interpret TSH levels, the perception that treatment of borderline thyroid patients is not medically advisable, and laboratories' failure to footnote or mention the new TSH reference ranges are all factors that do not serve patients well.

By default, under these circumstances, patients with a TSH level above 2.5 are likely to remain undiagnosed and untreated. And given that as many as 45 million Americans fall into this group, this represents a large number of people who could potentially benefit from thyroid treatment and aren't likely to receive it.

What Can Patients Do?

Ultimately, I feel there are three action points for patients to consider as we move forward.

1. Continuing Education.

I'm not seeing any evidence that we can safely sit back and assume that most doctors thoroughly understand the subtleties of hypothyroidism testing and diagnosis. In fact, given the disagreement among endocrinologists, and the lack of agreed-upon guidelines and lab ranges, there's even more need for patients to be knowledgeable about the lab ranges, informed about our own test results, and willing to discuss with practitioners their particular approach to diagnosis and treatment, and how it applies to our health. So my advice: keep reading, keep learning, and don't be afraid to ask as many questions as you need to in order to be sure you and your doctor are in agreement and working toward the same goal.

2. A New Practitioner.

When faced with endocrinologists or other physicians who are reluctant to diagnose by any other means than a rigid interpretation of the TSH results, it may be time to see a more integrative or holistic practitioner.

This may be a holistic MD or an osteopathic physician, or a trained and licensed naturopath, for example. In my opinion, some of the best thyroid care is provided by integrative practitioners who view TSH testing as only one component of thyroid diagnosis and treatment. These practitioners typically call on a range of approaches for diagnosis and management of thyroid disease, including:

  • Additional blood tests, such as Free T4Free T3, and antibody profiles
  • Clinical evaluation of visible signs of thyroid disease, including changes in reflexes, swelling and edema of the face and extremities, hair loss in head and body, loss of outer edges of eyebrows, among others
  • Clinical manual and visual examination for thyroid enlargement and nodules
  • Check of blood pressure and heart rate
  • Imaging tests to identify thyroid enlargement, atrophy, and nodules

Integrative practitioners who include more holistic approaches may also incorporate other diagnostic techniques, such as basal body temperature testing. A consistently low body temperature is considered a sign of hypothyroidism by followers of the theories of the late Broda Barnes, MD, a pioneer in hypothyroidism treatment. Some practitioners believe that saliva testing may be equally accurate -- or even more accurate -- than blood tests for some thyroid patients.

Closing Thoughts

Thyroid Awareness Month is coming in January. Each year, AACE adopts a theme and conducts a public relations and awareness campaign with the media to help focus attention on thyroid issues. In past years, the issue was doing a thyroid self-check of the neck, and the menopause/thyroid connection. While these PR campaigns can be helpful, I would like to see AACE spend its time and money focusing on an outreach campaign to the rest of the medical community. Let's see a campaign to educate all doctors about the symptoms of thyroid disease, and the fact that, as Dr. Garber said, "[TSH] values between 2.5 and 4 are more likely to reflect early disease. Though intervention is not necessarily called for, it may be called for on an individual basis."

Sources

"AACE Medical Guidelines for Clinical Practice for the Evaluation and Treatment of Hyperthyroidism and Hypothyroidism," Endocrine Practice, Vol. 8, No. 6, Nov/Dec 2002.

Demers, Laurence M. and Spencer, Carole A., Editors. "NACB Laboratory Medicine Practice Guidelines, Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease," National Academy of Clinical Biochemistry, 2002, Online

Fatourechi V, Klee GG, Grebe SK, et al. "Effects of reducing the upper limit of normal TSH values."Journal of the American Medical Association. 2003;290:3195-3196.

Garber, Jeffrey, MD, FACE. "Hypothyroidism--Talking Points 2006," US Endocrine Disease 2006

"New Campaign Urges People to "Think Thyroid" at Critical Life Stages and Get Tested," American Association of Clinical Endocrinologists, Press Release: January 18, 2001

"Over 13 Million Americans with Thyroid Disease Remain Undiagnosed," American Association of Clinical Endocrinologists, Press Release: January 2003

Shomon, Mary. "The TSH Reference Range Wars: What's "Normal?", Who is Wrong, Who is Right..." About.com Thyroid Site article, Online

Shomon, Mary. "Endocrinologists Say TSH Normal Range is Now 0.3 to 3: Millions More at Risk," About.com Thyroid Site article, Online

Shomon, Mary. "Does Your Doctor Know About the New TSH Normal Range?" About.com Thyroid Site article, Online

Shomon, Mary. "AACE Changes Position re: TSH Normal Range," About.com Thyroid Site article, Online

Shomon, Mary. Telephone interview with Dr. Jeffrey Garber, MD, FACE. August 16, 2006

Surks, Martin et. al. "Subclinical Thyroid Disease," Journal of the American Medical Association. Vol. 291 No. 2, January 14, 2004, Online

Surks, Martin. "Commentary: Subclinical Thyroid Dysfunction: A Joint Statement on Management from the American Association of Clinical Endocrinologists, the American Thyroid Association, and the Endocrine Society," Journal of Clinical Endocrinology and Metabolism,, 90(1): 586-587, 2005

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