Mito
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- Dec 10, 2016
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Small changes in free T4 result in a large change in TSH. For example a free T4 change from 1.0 ng/dL to 0.5 ng/dL will result in a TSH rise from 0.5 mIU/mL to 50 mIU/mL.
So large changes in TSH result in very small changes in free T4. For example, a rise in TSH from 1.0 mIU/mL to 5.0 mIU/mL reflects a drop in free T4 from 1.0 ng/dL to just 0.9 ng/dL.
Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care
http://clinchem.aaccjnls.org/content/clinchem/57/1/122.full.pdf
So large changes in TSH result in very small changes in free T4. For example, a rise in TSH from 1.0 mIU/mL to 5.0 mIU/mL reflects a drop in free T4 from 1.0 ng/dL to just 0.9 ng/dL.
Biochemical Testing of the Thyroid: TSH is the Best and, Oftentimes, Only Test Needed – A Review for Primary Care
http://clinchem.aaccjnls.org/content/clinchem/57/1/122.full.pdf