Uptake too low- and now TSH is up and I am hypo

[melpol]

Hello Dr. Lupo, and thank you for taking the time to read my question.  I will try to be as brief as possible- I was diagnosed as hyperthyroid in Jan- 07 and put on PTU.  Slowly my numbers were in normal range and after 6 months my endo tried taking me off to see if I would go into remission.  I went back to hyper within a couple months.  She then suggested RAI.  I went in to have an uptake dose and scan and was told that my uptake was too low to have the treatment (2%).  My doctor then put me back on PTU.  After two months my TSH was still unmeasurable, so she upped my dose.  The next month it was 8.4.  So she lowered my meds.  Then this month it is 9.1.  So she just lowered them again.  She says we will keep me on the PTU for another 6 months and try again to take me off and see what happens.

I have two questions out of all this:

Why was my uptake so low?  Nobody has given me any possible reasons why.  It would stand to reason being hyper that it should have been high, right?  

Is this plan of action by my doctor a normal progression?  Or should we be looking at other options?  I am so confused as to what to do.  My endo is a very well respected physician and comes highly recommended so I would like to trust her plan.

Any help you could give would be much appreciated.  Thank you!

[Mark Lupo, M.D.]

Hyperthyroidism with low I-123 uptake is caused by excessive iodine intake/exposure (ie CT scan or taking iodine supplement), thyroid hormone intake or thyroid inflammation.  While there is not a definite answer, the proper course is to titrate the PTU and follow the thyroid levels to see what happens.  It may be worth coming off the PTU to see what really happens, also of interest would be TSI and TBII which are markers for Graves disease.  If you are on a low dose PTU (50-100mg/day total), stopping it may reasonable with close observation.  Remeber, I-131 therapy is never an emergency, so it is important to make certain the hyperthyroidism is likely a consistent problem requiring definitive treatment;.

[melpol]

Thank you for your answer Dr. Lupo.  What you said makes perfect sense.  

I do not know what could have caused the low uptake, I was off the PTU for 2 months before, not on any supplements and had not had a CT scan.  Perhaps an inflammation?

Currently I am only on 50mg PTU (for the past two weeks since my last blood work).  I will see what happens to my levels when I go back, which I plan to do next week.

I will ask my doctor about the TSI and TBII, I have always been told I have Graves, but never knew the reason behind the diagnosis as I did not have "classic" Graves symptoms.  

Thank you again for taking the time to answer my question.