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The TSH Reference Range Wars: What's "Normal?", Who is Wrong, Who is Right...

And What Does It All Mean For You and Your Health?


Updated June 10, 2014

The TSH Reference Range Wars: What's "Normal?", Who is Wrong, Who is Right...
According to Wartofsky and Dickey, opponents of the new range argue against treatment for subclinical thyroid problems because they are concerned about risks of subclinical hyperthyroidism due to overtreatment. Wartofsky and Dickey argue, however, that there is an equivalent risk of undertreatment, and that all of these risks can be minimized by educating doctors about the desirable TSH target and teaching them how to use various dosages to reach those targets in patients. They write:

To us, individual failure on the part of physicians to appropriately monitor levothyroxine therapy and adjust doses is not a rationale to withhold the indicated therapy. We find the reluctance of the consensus panel to consider treatment for mild TSH elevations puzzling when it is most likely that they would not argue with the wisdom and rationale for early therapeutic intervention to mild diabetes mellitus with slight, but definite, elevations in blood glucose, mild elevations in low-density lipoprotein cholesterol, or mild elevations in blood pressure. After all, few endocrine disease states appear suddenly in an "on or off" or "black and white" manner. Rather, the disordered physiology must start at sub-intense level and then will have the potential to progress from mild to moderate to overt or severe. Just as we have revised downward our concept of normal range blood pressure and cholesterol, we new now should consider the evidence for doing so with TSH. Given the wealth of data on the abnormalities present in untreated subclinical hypothyroidism or hyperthyroidism and the demonstrated benefits of therapy to date, we are not disposed to have our hands tied by the deficiencies inherent in analyses of this issue by evidence-based medicine and allow our patients to continue to be at risk as a consequence."

They also conclude their article with what may be the most sensible statement of both arguments:

"...the decision as to whether to initiate a trial of levothyroxine therapy is based more upon the 'art of medicine' at this time than the science."

What's Normal, Anyway?

There is also an argument regarding whether or not fluctuations with the normal range -- by whichever standard, old or new -- represent thyroid dysfunction on an individual basis. Danish researchers found that each person tends to have what's known as a "set point," a particular level of T4, T3 and TSH that their body wants to return to automatically. We then tend to maintain thyroid levels around that set point, within a narrow range -- a range much narrower than the "reference range" for normal used by laboratories for testing.

Because each of us has a distinct set point for TSH, T3 and T4 levels, the general population references ranges are in fact too broad to detect changes to thyroid function that may represent disease in an individual.

The Danish researchers concluded that:

The distinction between subclinical and overt thyroid disease is somewhat arbitrary because it depends to a considerable extent on the position of the patient's normal set point for T3 and T4 within the laboratory reference range...In conclusion, we found that individual reference ranges for serum T3 and T4 are about half the width of population-based reference ranges. Hence, a test result within the laboratory reference limits is not necessarily normal for the individual.

>> What Does it Mean for You? What Should You Do?

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