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T3 before RAI

nate28
Posts: 5
Joined: Feb 2007

I have a question.

In preparation for my RAI Therapy I went of T4 4 week before the treatment and I went off T3 2 weeks before the treatment.

So I was on T3 for a total of 2 weeks.

This time around the Radiologist (a different one) wants me on T3 for 5 week (a significant jump).

My impression is that 5 weeks is not standard. Any thoughts?

Rustifox's picture
Rustifox
Posts: 131
Joined: Mar 2005

Hi, Nate
No, 5 weeks on LT3 is not standard - but sometimes there are extenuating reasons for this change in protocol.

Is this your second treatment? Perhaps they feel/felt that your TSH did not get high enough during your first treatment? (The higher the TSH, the more absorbtion of radioactive iodine). They may believe that you did not absorb as much of the RAI as you should have the first time around.

The 4 week protocol is relatively new - it used to be 6-8 weeks, generally 6 weeks as a 'standard'. A few years back, they did studies and found that many of us see a rapid rise in TSH when taken off our T4 - some of us very rapid - so many doctors began using the shorter protocol.

Another reason can be extenuating circumstances - that we have a health issue that makes it somewhat concerning to have a longer period completely off of hormones. For example, prior to my treatment, my doctor had me stop T4 for 21 days; I took cytomel for 11 days, and then followed by 10 days of zero hormones before treatment, due to a heart issue. Others sometimes use a 1/2 dose protocol - where they just cut the LT4 dose in half until the TSH rises to 30 (30 is the bare minimum TSH for RAI treatment - but again, higher TSH seems to better in some cases where absorption of RAI is low). Extenuating circumstances can also sometimes include simple 'timing' - that they can't get you sceduled for the RAI until after a certain date...unfortunately that happens sometimes, too.

Lastly, your radiologist may be using 'older' guidelines... so you really won't know for sure what the thought pattern is behind this until you question it, which I would certainly do. If you are having a treatment, it is also 'standard' to have a period of at least 10 days without cytomel/LT3 - most doctors go 2 weeks - so if that isn't built in to your treatment timing, I'd be asking about that, too.

Here is the information on the 'shorter' protocols for treatment and/or scan doses (in this case, a two week protocol), in case your radiologist is not familiar with this - there are numerous studies that have been done, showing similar results, one which indicated that 98% of patients achieved sufficient TSH within a 4 week timeline:
http://www.medicalnewstoday.com/medicalnews.php?newsid=6912

I would certainly ask the radiologist why the 5 week protocol for you; as this explains, hypothyroidism in preparation for our treatment and/or scans can have consequences:
http://www.eje-online.org/cgi/reprint/156/1/13.pdf

nate28
Posts: 5
Joined: Feb 2007

This is my second treatment. When I asked the doctor why the long period on T3 he said "normal protocol."

I think I see what is happening here. My first Radiologist was following the new guidelines, where 2 to 3 weeks on T3 and 1 to 2 weeks LID is recommended. My new radiologist is going with the older guidelines, where 4 to 5 weeks of T3 and 2 weeks of LID is recommended.

I guess I am okay with the older guidelines since I feel pretty good on T3. However, I am worried that whatever remaining tissue there is will grow with the increased time off T4, thus lessening the chance of success the second time around, which I want to be my last!

Thanks for your help.

purpleglitter
Posts: 3
Joined: Jun 2007

Hi. I am just new to this site and to having cancer of the thyroid. I saw a few of your posts and it seems that you have a wealth of knowledge. Would it be O.K. to be in contact with you through this site?

Rustifox's picture
Rustifox
Posts: 131
Joined: Mar 2005

Please feel free to email anyone here to help you, purple; there is a little 'email/letter' icon on the bottom left side of every post box; just click on that, and they will send us an email in the internal CSN mail system.

Rustifox's picture
Rustifox
Posts: 131
Joined: Mar 2005

Here is another one of those 'shorter duration' hypo studies, better 'proof' in case your radiologist just isn't familiar with shorter withdrawals:
http://jnm.snmjournals.org/cgi/content/abstract/45/4/567

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