blood test for thyroid function TBG, anyone know what this test is for? : Thyroid Disease : Active Low-Carber Forums

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chemong932

Wed, Nov-20-02, 15:04

Hi!
I am new to this site. I have been searching through various sites looking for information on what the blood test TBG is for. My doctor added it to the list of thyroid function tests that he occasionally orders. Thank, Melanie

doreen T

Wed, Nov-20-02, 17:47

hi there,

A good search engine is always helpful ;) .. I entered "TBG thyroid" into Google, and got 3,050 results.

Here's some info about TBG (Thyroid Binding Globulin) from Endocrineweb.com (http://www.endocrineweb.com/tests.html):Thyroid Binding Globulin.

Most of the thyroid hormones in the blood are attached to a protein called thyroid binding globulin (TBG). If there is an excess or deficiency of this protein it alters the T4 or T3 measurement but does not affect the action of the hormone. If a patient appears to have normal thyroid function, but an unexplained high or low T4, or T3, it may be due to an increase or decrease of TBG. Direct measurement of TBG can be done and will explain the abnormal value. Excess TBG or low levels of TBG are found in some families as an hereditary trait. It causes no problem except falsely elevating or lowering the T4 level. These people are frequently misdiagnosed as being hyperthyroid or hypothyroid, but they have no thyroid problem and need no treatment.
hope this helps,

Doreen

mbschlgr

Thu, Nov-21-02, 10:48

Originally posted by doreen T

Direct measurement of TBG can be done and will explain the abnormal value. Excess TBG or low levels of TBG are found in some families as an hereditary trait. It causes no problem except falsely elevating or lowering the T4 level. These people are frequently misdiagnosed as being hyperthyroid or hypothyroid, but they have no thyroid problem and need no treatment.

Exactly! My dr. ordered it because I am on 175mcg of synthroid. My TSH was always showing normal but they needed to supress is due to nodules and goiter... my levels of TSH show me to be hyperactive, and my T4 shows to be low in spite of the amount of med, but the TGB shows that I am acutually Hypothyroid!!! confused now??? :confused: She said in many cases "levels" mean nothing...

Thyroid is a very person specific problem. They are changing many of the past normal ranges etc.