Even though recommended changes to clinical laboratory standards for the thyroid stimulating hormone (TSH) "normal range" were announced in 2002, your doctor probably is still
unaware that a major revamping has been done to this reference range. The TSH test, which continues to be the primary blood test used by conventional doctors to diagnose thyroid disorders, is still a subject of great disagreement and controversy for experts.
Until 2002, the standard was that the normal range for TSH at most laboratories has fallen in the 0.5 to 5.0 range, with hyperthyroidism being below .5, and hypothyroidism above 5.0.
The guidelines, however, recommend that the range for acceptable thyroid function, and thyroid treatment, shift to a TSH of 0.3 to 3.0, which is a far narrower range.
The American Association of Clinical Endocrinologists estimatd that the new guidelines actually double the number of people who have abnormal thyroid function.
What to Send to Your Doctor
Since your doctor is likely to say "I haven't heard anything about these new changes," or "the lab is still showing .5 to 5 as the normal range, and I'm not changing anything until the lab does," you will want to send some materials to your doctor ahead of your next appointment. These include the following:
1. January 2003 Press Release from the American Association of Clinical Endocrinologists
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Highlight the third paragraph for your doctor. this paragraph reads:
"Until November 2002, doctors had relied on a normal TSH level ranging from 0.5 to 5.0 to diagnose and treat patients with a thyroid disorder who tested outside the boundaries of that range5 . Now AACE encourages 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. 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."
2. The National Academy of Clinical Biochemistry, part of the Academy of the American Association for Clinical Chemistry (AACC), Laboratory Medicine Practice Guidelines: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease
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You may want to highlight the sections that read:
"It is likely that the current upper limit of the population reference range is skewed by the inclusion of persons with occult thyroid dysfunction."
"In the future, it is likely that the upper limit of the serum TSH euthyroid reference range will be reduced to 2.5 mIU/L because >95% of rigorously screened normal euthyroid volunteers have serum TSH values between 0.4 and 2.5 mIU/L."
"A serum TSH result between 0.5 and 2.0 mIU/L is generally considered the therapeutic target for a standard L-T4 replacement dose for primary hypothyroidism."
"Thyroxine requirements increase during pregnancy. Thyroid status should be checked with TSH + FT4 during each trimester of pregnancy. The L-T4 dose should be increased (usually by 50 micrograms/day) to maintain a serum TSH between 0.5 and 2.0 mIU/L and a serum FT4 in the upper third of the normal reference interval."