Giraffe
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I highly recommend reading the full article, there is a lot of information and advice on that site.
Some excerpts:
What is a reference range? Changing the reference range.
The two sides of the public debate
Wartofsky & Dickey, "Controversy in Clinical Endocrinology: The Evidence for a Narrower Thyrotropin Reference Range is Compelling," Journal of Clinical Endocrinology and Metabolism 90(9)/5483-5488
Some excerpts:
What is a reference range? Changing the reference range.
Reference range is a critical component, and the validity of the entire TSH test as diagnostic tool depends on it. A TSH reference range is obtained by taking a large group of people in the population, measuring their TSH levels, and calculating a mean value. Supposedly, these people should be free of thyroid disease, so that the level represents the mean TSH of a typical thyroid disease-free person in the population.
The reference range is what determines whether or not thyroid disease is even diagnosed at all, much less treated, and when it is diagnosed, how it is treated.
After noticing that patients who had TSH levels in the higher end of the normal range tended to go on to develop hypothyroidism more often than those in the lower end of the spectrum, researchers delved more fully into understanding how valid were the reference ranges in use. They found that the upper TSH normal range has traditionally included people who have mild thyroid disease, and their higher TSH levels skewed the standard curve, potentially making the reference range wider than it should be, and excluding some people who legitimately had a thyroid condition.
These findings led to the recommendation in January 2003 by the American Association of Clinical Endocrinologists (AACE) that doctors "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 two sides of the public debate
Surks, Goswami and Daniels base their argument on their assertion that "because routine levothyroxine treatment is not recommended for subclinical hypothyroidism, it is certainly not warranted in individuals with upper reference range TSH [TSH 2.5 to 4.5].
The authors also state "The only documented adverse health outcome for individuals with TSH levels between 3.0 and 5.0 is progression to overt hypothyroidism. Levothyroxine treatment would clearly prevent that outcome, but at what price?"
However, it must be asked, why is preventing progression to overt hypothyroidism not a desired health objective, given that overt hypothyroidism most definitely can contribute to obesity, heart disease, depression, infertility, and host of other health problems?
Drs. Wartofsky and Dickey argue that the previously accepted reference ranges are no longer valid because the reference populations previously considered normal were "contaminated" with individuals with various levels of thyroid disease. They argue that the benefits of treatment far outweigh any minimal risks.
......In their article, they point to some key facts, including:
- In an iodine-sufficient population, the mean TSH is 1.5
- In African-Americans with low incidence of Hashimoto's thyroiditis, the mean TSH is 1.18, which suggests that "this is close to the true normal mean for a normal population"
- When people with positive antithyroid antibodies or family history of autoimmune thyroid disease are excluded from the "reference range" cohort, the normal reference range becomes .4 to 2.5
Wartofsky & Dickey, "Controversy in Clinical Endocrinology: The Evidence for a Narrower Thyrotropin Reference Range is Compelling," Journal of Clinical Endocrinology and Metabolism 90(9)/5483-5488