# difference between thyroglobulin and AB anti-thyroglobulin



## nichristeve

I have read a bit about thyroglobulin as a cancer marker....mine was high 263, and I do have papillary carcinoma. But I was just looking at my labs and they state:
thyroglobulin 263 
AB Anti-thyroglobulin < 20

Can anyone tell me the significance of these tests? thank you so much for your help!


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## joplin1975

http://labtestsonline.org/understanding/analytes/thyroglobulin/tab/test

A thyroglobulin antibody (TgAb) test is typically ordered along with the thyroglobulin test. Thyroglobulin antibodies are proteins produced by the body's immune system to attack thyroglobulin. These antibodies can develop at any time. When they are present, they bind to any thyroglobulin that may be present in the blood and interfere with the interpretation of the thyroglobulin test. Once they have developed, they will not go away and from that point forward will affect the usefulness of the thyroglobulin test.


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## teri2280

Joplin gave a great answer, of course, but I would like to add that chances are that if you have the antibodies, a smaller hospital system will NOT be able to truly read your Tg results. The Antithyroglobulin ABs, if you have them (not all of us do, but I do), bring down the "true" Tg amounts. My Tg tests have to be sent to USC to get an accurate read on them. It's a PITA, but in some of us lucky ones, it has to be done. I THINK that the Mayo clinic is another place that has the means to get an "accurate" read on what our Tg levels really are, my endo just chooses USC over Mayo for their turn around time, which is about 1 week vs. 6.

*Add* Your Antithyroglobulin AB number sounds about right. I'm looking at my most recent bloodwork, and the range for that is 0-40 IU/ML. My ABs are currently at 66, which is what makes my stuff have to be sent to USC. I don't know for sure that you won't get a true Tg reading because of your AB rate, but mine has to be sent out since it's so high. (I'm a weirdo that has them occur naturally, from what my endo says. Well, he didn't call me a weirdo, I added that myself. )


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## LaHa411

ahhhh I'm still so confused! Even if your TgAB is out of range do they still just monitor the tg as a marker for thyca patients? I'm 5 weeks post TT my Tg came back 2.10 range 3.00-40.00 but my TgAB is 1.9 range .0 - .4


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## joplin1975

I think it's different for everyone, but interestingly enough (at least for me) is that my team didn't test for thyroglobulin after surgery. They said the antibodies were too high to make it "worth" anything. They were more interested in the pre-RAI scan and felt that was more accurate.

I am having thyroglobulin pulled next week for my annual scan, but the radiologist said it was "just a piece of information [he] would consider" in concert with the scan results.

In short, they weren't putting too much credit into it because all my antibodies were so high. I'm not sure 1) how high the antibodies have to be to skew the results and 2) how the tg will play out for me in the future.

Not exactly helpful, I know, but...


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## LaHa411

Thanks Joplin- I just heard back from my Dr. and he said since I have positive antibodies it lets them know that the Thyroglobulin is not an accurate test until the antibodies clear which should happen overtime thus they will be rechecking periodically. So this basically tells me nothing lol. I guess I will just have to wait for the RAI scan. I have to say all this waiting and not knowing is really annoying!


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