I responded to your PM follow up question but thought I should post my response here too in case someone else is in you (and my) shoes with an increased Tg level following surgery and I-131:
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If someone has had multiple doses of I-131 it should take the Tg to "undetectable". "Essentials of Thyroid Cancer Management, Amdur, Mazzaferri, eds"
My sister had to go through three doses of I-131 before her Tg level became undetectable. Last month was her 5-year mark and they put her through the thyrogen shots to check her levels again and it still came up as "undetectable". Mine isn't there yet and my endo is planning another course of I-131 for me this summer.
Here is a link to an on-line endocrinology journal: http://www.*****************/endocrinology/articles/thyroid/thyroglobulin_cancer/
The quote from the article that pertains the most to your (and my) situation is: "With all thyroid cells eliminated, the Tg level should be zero, and its presence later signals a possible return of the disease. (Sometimes, however, low levels of Tg can be present following treatment, and slowly decline over time.)"
This is from Labtestonline.org (a site that explains blood tests in layman terms): "Small amounts of thyroglobulin are normal in those with normal thyroid function. If thyroglobulin concentrations are initially elevated in a person with thyroid cancer, then it is likely that thyroglobulin can be used as a tumor marker. Thyroglobulin levels should be undetectable or very low after the surgical removal of the thyroid (thyroidectomy) and/or after subsequent radioactive iodine treatments. If levels are still detectable, there may be normal or cancerous thyroid tissue remaining in the person's body, indicating the need for additional treatment."
And this is from Thyroid.org: "blood tests are done to measure the levels of T4 and TSH as well as a thyroid cell protein, thyroglobulin, which serves as a thyroid cancer marker. The thyroid hormone dose is adjusted to lower the TSH level into the low range. If the thyroglobulin level is still detectable despite a TSH in the low range, it means that there still are potential thyroid cancer cells functioning in the body"
That's why I was asking if you had a good endocrinologist. Most cancer centers don't deal with thyroid cancers and aren't up on all of the latest tests and studies. The "normal range" for thyroglobulin for everyone else is VERY different than what is wanted for thyroid cancer patients. We don't have a "normal range". You need a good endocrinologist who specializes in thyroids.
After surgery and two rounds of I-131 radiation your Thyroglobulin (Tg) level should be "undetectable" or very close to 0.2. Request Thyrogen shots to see how high the Tg level goes and anther I-123 scan would be a good call too.
Many cancer centers don't treat thyroid cancer - even my oncologist (who works at the largest cancer treatment center in Utah) refers thyroid cancer patients to an endocrinologist. Do you have a good endocrinologist who specializes in thyroid conditions (most don't)?
You really need more testing. If my endo saw my Tg level at 2.1 he's have me in the hospital immediately for another dose of I-131.
There are lots of thyroid cancer patients on the Thyroid Support group page who can also help and some referrals to good endocrinologists.
My gut feeling, they didn't get everything with the I-131 treatments and you are due for another.
Utahmomma
papillary carcinoma '03, second surgery '04, recurrence and I-131 '06
three sisters with papillary carcinoma (including one with three recurrences and I-131 treatments)
another sister and daughter with precancerous thyroids (removed)
I also forgot to say back in 2005 I had a total thyroidectomy