• Antibodies causing false thyroid levels

    Asked by Angelina05 on Friday, August 17, 2012

    Antibodies causing false thyroid levels

    I'm on a super high dose of synthroid and started to think that maybe I was being overmedicated, however my levels have FINALLY (after 6 years) leveled out at a "normal" range. Talked to my doctor this week and she mentioned that some thyroid cancer patients have certain antibodies in their system that cause routine bloodwork to show a wrong level of TSH and T4....she said there was another more detailed test to check my levels. Has anyone had expierence with this?

    2 Answers from the Community

    • nancyjac's Avatar

      I've been on synthroid of about 8 years now. The first 3 years were periodic increases in dosage and then stabilized for a while but now going through that process again since last year. I've had multiple test for TSH, T4, T3, and antibodies tests. However, the antibodies test does not have to do with you TSH level but rather to determine the cause of hypothyroidism. Hypothyroidism caused by destruction of thyroid function from these antibodies is called auto-immune thyroiditis or Hasimoto's thyroiditis. Cancer really doesn't have anything to do with it. Many people with auto-immune thyroiditis have never had cancer. Maybe your doctor is talking about different antibodies, but I've never heard of them causing errors in measuring TSH and it just doesn't seem logical to me that it could. However, it does make sense to me that the presence of some cancer antibody could be temporary based on your cancer or your treatment for it, and that could account for changes in your TSH levels but they would still be accurate for the time at which the blood was drawn.

      about 8 years ago
    • polytechnic's Avatar

      An anti-TSH antibody can attach to TSH and form a complex called macro-TSH. That indeed can interfere with TSH blood tests. I think that some methods of testing are better insulated from this than others. But you need more knowledge than I have to find out which, etc.

      However you need to be aware that there can also be antibodies to T4 and to T3, as well as the 'usual' thyroglobulin and thyroid peroxidase.

      And it may be important to realise that the antibodies themselves do not attack things. TPOab and TGab are indicative of attack on a thyroid by, usually, autoimmune processes. But they can also appear transiently after neck injury (surgery or strangulation) and in those cases will usually reduce over time.

      about 8 years ago

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