Presence of Tg. while on Levothyroxine after T/T for PTC

I would like to know whether a normal blood test would show Tg result
while I am on Levothyroxine 125 mcg even though I do not have thyroid as it has been removed for PTC 2 years ago.
Recently I went for a complete blood profile and my Tg was shown as 48
(Reference Range : 0.0 - 78). I told the doctor that I do not have the thyroid
and that the Tg result should be near undetectable or '0'. He told me, not necessarily as I am on Levothyroxine and that the Tg result would appear.
Is he right?
Anyone out there, please let me have your experience or opinion.
Thank you.

Sanjay5

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I had my thyroid removed ten years ago and have had an undetectable Tg until August 2013. I too have been on Levothyroxine for the past ten years. Blood test in August had a Tg of .5. Two subsequent blood test have shown Tg at .8 and .4. Had another blood test this past Friday but do not yet know results. My endo says that I have Tg rising negative scan disease. Endo further states that because Tg is rising (detectable) my thyroid cancer is back - somewhere. WBS and U/S have not yet showed anything. If Tg spikes significantly (above 2), endo says he will send me for PET scan and if that does not isolate where the cancer is I will probably get a RAI treatment. I hope this information helps. Please let me know how things develop. And I too would apprecitae hearing from anyone else in this position or what your thoughs might be on this. Thank you.

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Levothyroxine pills do not contain thyroglobulin, so they can not raise your Tg. Natural thyroid, or animal derived thyroid hormone replacements do contain thyroglobulin though many people digest it and the Tg does not rise, but it can on natural thyroid only, not on synthetic hormone replacement. If on synthetic hormones, Tg can only come from thyroid remnants and thyroid cancer cells, or shows from test errors such as interference from TgAB or HAMA.

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What BiomedEE said. I would request a repeat test for verification and get a second opinion if your Tg is still elevated.

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Agreed with above.

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Just for all your information, about 2 months ago I had a complete test specially for the Thyroid and the results
showed that my initial TgAb from 17.8 dropped to <10 but my Tg rose from the initial 13.4 to 17.4 (range as mentioned
in the pathology report for T/T of PTC patients - 0.0 - 20).My Free T3, FreeT4, TSH suppressed to 0.1 and my Chest X-ray,
Ultrasound of the Neck and WBS (with tracer dose 5Mci) all came out clean.
Its best that I seek a second opinion from another Onco to ensure that I am on the right track of treatment. Mostly likely,
a PET Scan would help to identify my problem. This PTC as many say is a good cancer but appears to be very uncertain
and makes one 'go merry go round'.

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I just had a 3mci RAI WBS last Thursday and the results according to my doctor were "Negative for functioning residual tissue in the neck or metastases of the body - no need for ablation since no tissue seen". The US was also negative. I have positive rising TG/TGab which is what started the testing. I had PTC in 1982 with partial removal and the remaining removed which was Hashi's in 1990. I never had RAI ablation so how can there not be some residual tissue and why are my Tg rising? I asked my Endo the same question in an email Friday and have not had a response. What is next? I have been on Synthroid for years and I am also taking Cytomel now. My TSH is .047. My last Tg was 2.1 and the Tgab was 152.1. For those of you who have gone for a 2nd opinion, what did they do differently?

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Hai jkittie - Many of us find this PTC so uncertain. Today it is almost gone (Tg) and the next moment you find it is there. I had T/T about 2 years ago - had RAI (100 mCi) but my Tg is now 17.4 and my TgAb is <10. I am on Levothyroxine 125 mcg for the past 2 years.
My TSH is suppressed to 0.18.Anyway I have decided to get a 2nd.opinion and also go for a Tg test in a different lab and move on
for further tests like the PET scan and d still findings, I intend to keep my TSH suppressed and live the best I could. I am getting
exhausted with all kind of testing and treatments.

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jkittie, Yours may well be just TgAB issues I don't have experience on that so let other chip in on that. For second opinions some of the imaging options are PET, PET/CT, and the latest model spiral CT with high dose iodine contrast. There are advantages to each, I tend to favor the latest spiral CT for low Tg because they have the highest resolution (not the older CT or even old spiral CT so just the contrast spiral CT of last few years). Pet uptakes glucose, perhaps better at higher Tg values.

Hope you find answers..

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I had my thyroid removed in 2009. All my lab results were ok for 3 yrs then Tg started to increase slowly. Now my TG level is 299
Had it investigated. PET/CT scan done and seen nodules in my lungs. Had lung biopsy and confirmed it metastasized to my lungs.
I'm being monitored and ct scan every six months. I think Tg is a hormone secreted by thyroid. Good luck to you

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I still haven't heard back from my dr. Maybe she is waiting on the suppressed Tg before she answers me. Thank you for your input. On one hand I am relieved that the WBS was clean but on the other, not satisfied with those numbers. I will get a second opinion if she doesn't have a plan.

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