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Old 01-23-2013
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Default TBG levels?

Hard to understand how an increase in TBG levels to an increase in total T4 and total T3 leads... (some mechanism.. something like feedback?)
in this case, the level of free thryroid hormones remain normal?? how then...?

Please, could any one help me?

thanks in advance.
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Old 01-23-2013
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Total serum T4= TBG-bound T4+ Free T4 (unbound)

An increase in TBG synthesis means that now we have more proteins to bind the free T4/T3 in the body. because of that, we will have an initial decrease in our FREE T4 levels (remember T4 has a high affinity for TBGs). However, T4 levels in our body are highly regulated, so this will soon be compensated for by T4's negative feedback mechanism which activates TSH--->Thyroid---> More Free T4 to restore the normal amount in blood. This is why when you do a blood test for example, the total serum T4 level will be increased (you've increased the number bound to TBG's), but the free T4 levels are going to be normal.
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