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Diabetes

Thyroid confusion

08/10/2009

Question:

I have had my thyroid tested. My T4 is 12.7, my T3 is 163 and my tsh is 1.93. One of my doctors told me that I have inactive thyroid and my General doctor said that I have overactive t4 thyroid. All my symptoms match under/inactive though.. Im very sensitive to cold, tired all the time, have constipation sometimes and gained weight. I though that thyroid test are opposite of what you think, meaning if the test results are in high range, you are low on thyroid levels and you are underactive? Im so confused. I think my reg doctor is wrong/.

Answer:

It depends on exactly which tests were used and what country you are in.  I cannot be sure but it looks like the T4 test is a total T4 and the T3 a total T3.  If that is the case and these were from a US laboratory, then there may be some confusion because there can be variations in proteins in the blood which bind thyroid hormone, resulting in an alteration in total hormone level that is not an accurate representation of the free or unbound or active thyroid hormone level - that sounds like what the first doctor might have been trying to explain to you.  A common scenario would be to have an increase in thyroid binding proteins from pregnancy or the use of a drug or exposure to estrogen resulting in increased total T4 and in some cases increased total T3 while the free hormone levels are normal and the TSH normal.  You may need a second opinion to clarify this.

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Response by:

Robert M Cohen, MD Robert M Cohen, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati