how to interpret thyroid labs?

I saw my doctor (a Hertoghe doctor) last week. My thyroid labs (from two weeks ago):

TSH <0.01 (0.2-4.0)

FT3 2.2 (1.2-4.3)

FT4 0.9 (0.8-1.5)

My doctor said that, as long as my TSH remains low, that shows that my thyroid meds are working, and that FTs are individual, constantly fluctuating and don't mean anything. This came as a surprise to me, as I have always been told FTs levels are the most important thing when deciding whether you are optimally treated...

I am currently on Thyroid-S (7 grains daily). My doctor prescribed Erfa, but I am not sure if it would be a good idea to try that far, Thyroid-S has worked well, although I seem to require a lot. But after all the problems with Erfa I am not sure I should go down that's quite expensive in Belgium compared to Thyroid-S, and it would have to work really well in order for me to be willing to make the switch...

Since weaning off Medrol for adrenal fatigue six months ago I have noticed an increased need for NDT...but I'd hate to go back on Medrol after finally being able to wean off it.

10 Replies

  • Anna69,

    I'm surprised to hear that a Hertoghe doctor thinks TSH is more important than FT4 and FT3 in determining optimal dosing.

    If you are happy taking Thyroid-S and it is less expensive than Erfa why consider switching?

  • Thyroid-S has unknown content although I assume it has a fair amount of T3 and some T3. Thus you would expect your fT4 to be low. Your fT3 would depend upon how frequently you take the Thyroid-S (twice a day or once daily?) and the time interval between the last dose and having the blood taken. Given these variables (and Thyroid-S may vary from batch to batch?) the only biochemical result you have to go on is the TSH, which of course is not ideal.

  • I take it once daily (in the morning). I have been wondering if Erfa would result in higher FTs and more stable hormone levels...?

  • So you left 24 hours between your Thyroid S and the test? That's why the FT3 is so low.

  • Meaning it would be a good idea to take my meds before going to the lab...? Anyway, I guess that would give a better picture of what my FT3 levels really look like...I have always avoided that while on meds containing T3 as most doctors freak out at the sight of high FT3 levels...

  • No, I meant take your last dose 12 hours before the test. I certainly wouldn't take it on the morning of the test, but the night before...

  • Yes, I take L-T3 twice daily and have the blood taken in the morning. I then mentally add about 10% to the fT3 figure to get a guess of the real average level. If you take it once daily then having the blood taken about 10 hours later would give a reasonable figure, assuming the half life is about 24 hours. It's a bit hit and miss as noone knows the T3 half life in an individual patient. Also the half life will shorten as fT3 levels rise as type 3 deiodinase increases. It's not a science.

  • It's an art! lol What a pity doctors aren't artists! But, they're not scientists, either. Neither use nor ornament, I say!

    Yes, Anna, the day before the test you could take your Thyroid S in two doses, so that the test is 10 to 12 hours after the dose.

  • Thanks:-)

  • Hi,

    I'm pretty new with under active thyroid, (18mth). My doctor started me off with 25mg. A few weeks later I was an inpatient and they told me that my thyroid test was a little high, (T4.9 which I don't know what it means and still don't). The doctor told me to see my GP in weeks to check my thyroid levels. Because I was so unwell, a PE, then a thrombosis, my hair was falling out etc, it was put down to my anticoagulant treatment. A year later, hardly no hair, I was lost in the thyroid system and they put my thyroxine to 100mg, but my hair is still falling out, after 3weeks it's still just over T4.9. How long does it take to get your thyroid levels to even out. I can't afford to lose anymore hair. Please help.


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