[Anonymous]

#1020295

How can my T3 and T4 numbers be within range, but my tsh be low .109. I thought one or the other have to be out or range for this to happen?

[Anonymous]

#1076619

The TSH is a “moving average’ of our thyroid hormone levels. So at the moment in time that your thyroid levels showed “normal”, your TSH can indeed show that over time, they were out-of-whack. The TSH test is thought to be “finer” — i.e. be able to show more minute quantities of TSH accurately — so our doctors do tend to rely on it.

Bobbi — NGDF Online Facilitator

[Anonymous]

#1076620

I had RAI about five months ago and just had my TSH/Free T4/T3 re-tested recently.

My TSH at the time of the test was 40 (better than the 53 it was at the last test six weeks ago, but still way out of whack), and my Free T4 was normal. I was a little confused by this, too, because my TSH was so far out of normal. I’m assuming that the doctors really only use TSH as a measurement for adjusting meds, so why do they order T3 and T4?

[Anonymous]

#1076621

Hi slb,

T4 results can be helpful in the early stages (first year, for instance) after RAI. TSH is like a running average, giving a general idea of where our levels have been for the past few months, but T4 is a more “current” reading. Looking at TSH and T4 together can provide a clearer picture of what’s going on, especially when the RAI is still working (which can take up to six months). Adjusting meds using only TSH as a guideline can work well as long as the patient waits at least six weeks between changing doses & getting tested, but testing any sooner or trying to identify any anomalies in levels would usually trigger a doctor to ask for T4. T3 is really a flash in the pan (changes hourly depending on our immediate needs for thyroid hormone), but it can provide valuable information if our T3 is chronically low. TSH is always tested. T4 sometimes. T3 rarely. I hope that makes sense!

~Ski
NGDF Assistant Online Facilitator

[Anonymous]

#1076622

One of the reasons we don’t try to interpret test results here is that there are a lot of complexities, and none of us are expert enough to navigate them. So, anything said here is a guess.

We’ve been told at various times that the TSH is one of the last measurements to come into the normal zone. I call the TSH test a “moving average” of actual thyroid hormone levels, because if the thyroid hormone levels are for several days and normal for one the day of the test, the TSH will still show that the TSH is too low. It takes lots of days in normal for the TSH to settle into normal.

So, my guess is that analyzing for free T4 and T3 gives the doctor an idea of the “direction” in which thigns are progressing. If those free hormones are at the hypo end of the scale, vs. the hyper end of the scale, the adjustments to replacement hormone dose would be changed, accordingly.

Bobbi — NGDF Online Facilitator

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