What is the significance (if any) of low T3 only?

[MidwesternMom]

I've been on synthroid for years.  Recently had full thyroid panel (not just tsh like usual).  The results were a bit unexpected, but perhaps I am not properly understanding these hormones.  TSH was lowish but within range (0.3, I believe.)  T4 was well within range, but still in the lower half of the range.  T3 was low and out of range... barely, but out of range.  Do I need more or less synthroid?  Is this indicative of a pituitary issue?

(I'm bring sent to an endo for suspected pituitary issue, but not thyroid.  Based on t4 and tsh doc says thyroid is fine.)

I have never felt an improvement in hypothyroid symptoms.  I have a low body temp of 96.8 and a rhr of about 50- 55. Other things too like fatigue and other typical hypo issues.

So... any ideas?  :)  Why is t3 meaningless?  Why do they even check it if they don't care when it's out of range?

Thanks!!

[MidwesternMom]

Thank you, gimel!  That was extremely helpful!!  Thanks for the great info and excellent advice!!  :)

[gimel]

Having a relatively low TSH and T4/T3 at the same time is frequently indicative of pituitary problems, such that the thyroid glands are not receiving an adequate signal from the pituitary to produce more thyroid hormone.  

I'd have to disagree with your doctor that thyroid is fine.  It would also have been far more revealing of your situation if the doctor had run FT3 and FT4, as Stella was asking about.  At any rate, the doctor apparently doesn't realize that the ranges for T4 and T3 are too broad.  Results in the low end of the ranges frequently are consistent with hypo symptoms.   Symptom relief should be all important, not just getting test results anywhere within the ranges.  You can find some good info about this on this link.

http://www.hormonerestoration.com/Thyroid.html

In my opinion the best way to treat a thyroid patient is to test and adjust the levels of FT3 and FT4 with whatever type of medication is necessary to relieve symptoms, without being constrained by resultant TSH.  A doctor that will treat you clinically in this manner is what I call a good thyroid doctor.  Just because a doctor is an Endo does not mean that he will be a good thyroid doctor.  Frequently they specialize in diabetes, not thyroid.  Others have the "Immaculate TSH Belief" and don't want to treat your symptoms.  

I think that rather than waiting to find out about the Endo, I would call the office and say that you have a couple of questions before making an appointment.  Then ask if the doctor is willing to test and adjust free T3 and free T4 levels with whatever type of meds are required to relieve symptoms.  The other question is whether the doctor is willing to prescribe meds other than T4 types.  If the answer to either is no, then I would keep looking for a good thyroid doctor.

[MidwesternMom]

The t4 says it is free.  I don't know about the t3... it just say's t3 on the paper I have.  So I guess whatever the standard is, that is probably what they ran.

[stella5349]

Are these labs indicated as "free" T3 and "Free" T4?