new vs old FT4 range

[samking5]

Hiya,

my older ft4 blood results used the scale 10.5-24.5, whereas now they are 12-22, I was was wondering if this means that each point as a percentage is actually now worth a bit more, eg 1 point is worth 10% change vs 7% or that they are just saying they think outside 12 or 22 is not normal.

the reason I am asking is I am very sensitive to being overmedicated (even if it is 5/10% too high. and recent results have been around ft4 23 and i am really not feeling good. im wondering if this result is actually equivilent to 25 or 25.5 on the old scale eg 10% over the range.

[Lalatoot]

Samking the new range is the new range. The change of range means that the testing equipment has been upgraded. The ranges are based on the testing equipment used and calibrated using data from the local population.

To compare the old and new results you need to calculate percentage through range. So your old result might have been ft4 17.5 50% - if you are looking to maintain ft4 at this level you'd be looking for ft4 17 which is 50% through the new range.

Yes you are correct in thinking that your new ft4 result of 23 is 10% over range and the equivalent of being 25.9 (10%over) on the old range.

[samking5 in reply to Lalatoot]

ok so it 22.9 on the new range is effectively higher than the old range? I think my ideal are is somewhere around 19-20, but for me the upper end is very dangerous as if i tip over say 100% of what I should be on at any point in the day it activates really bad hyper symptoms. I do a lot better mildly undermedicated, even with my tsh perhaps 7-4. I am also realising my Ratio of ft4 to ft3 is bad, in fact it seems higher my ft4 the lower my ft3. I am not sure if a lower dose of ft4 + a touch of ft3 would actaully be best for me.

[Lalatoot in reply to samking5]

If you are 10% over in one range you should in theory be 10% over in the other range. 10% of the old range is 1.4 (the difference between the bottom of the range and the top of the range is 14) so you would be 25.9 on the old scale.

There is a link between high ft4 levels when on levo only and cancer. healthunlocked.com/thyroidu...

If my results were always at the top of the range, I would be considering reducing levo and introducing a little lio T3.

[samking5 in reply to Lalatoot]

thanks for your reply. I will check out that link. yes it seems whenever we try to respond to the tsh being a bit high by increasing levo it pushes my ft4 too high. the best periods ive had my tsh has been between 7-4. I wonder if the levo only is not mimicing my body's natural state. meanwhile my ft3 when diagnosed was 5.6 with ft4 of 16 (tsh 20) but has actually tended to be around 5 regardless of ft4, however the last test was 4.3 with the ft4 over the range! so the ft3 is not crazy low but in comparison the ft4 it is in fact there seems to a weird kind of inverse relationship the higher the ft4 the lower the ft3

[Lalatoot in reply to samking5]

Sam that's how the body works. It is a safeguard mechanism to stop the active hormone t3 level getting overly high.When the body senses that ft4 is higher than it likes, it downgrades conversion of t4 to t3 and increases conversion of t4 to reverse t3. So a higher ft4 can result in a lower ft3 as more is converted to reverse t3.

[samking5 in reply to Lalatoot]

oh wow that is very interesting! so a lower that what I would expect ft3 actaully could indicate the body is struggling with the level of ft4 then? interesting

[Lalatoot in reply to samking5]

Like everything else we are all different and no one can predict the level ft4 has to reach for their body to start convert more into reverse t3 rt3.There is a theory that for some even the spike as their total daily dose enters the system, is high enough to affect conversion. These folks can find benefit by splitting their daily levo dose into 2. This means that the spike in ft4 is reduced thereby avoiding that rt3 trigger and improving their results. This is only found out through trial and error.

[samking5 in reply to Lalatoot]

yes you are correct. I am wondering if i had a small amount of lio that would bring down my TSH while not spiking my ft4 too high. I think a small dose wouldnt risk the ft3 going over range, probably worth a try anyway if i can get a prescription.

[Lalatoot in reply to samking5]

Sam taking t3 slightly reduces ft4.

I was on 100mcg levo only. My TSH was below range; my ft4 at 60% and my ft3 at 17%.

I added 7.5mcg t3 to my 100mcg levo. This made my TSH undetectable; my ft4 at 50% and my ft3 72%.

Just to give you an idea of how a little can help.