T3 before RAI

Rustifox said:

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