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Dr. David
Dr. David, Board Certified Physician
Category: Medical
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Experience:  Experienced Physician trained in New York City. I'm ready to help.
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My T3, Free, Dialysis, LC/MS-MS lab results just came back

Resolved Question:

My T3, Free, Dialysis, LC/MS-MS lab results just came back as 1.23 pg/ml. This is much lower than the reference range. What does this mean?
Submitted: 10 months ago.
Category: Medical
Expert:  Dr. David replied 10 months ago.
Hello, this is Dr. David. I have read your question and I'm ready to help.

T3 can be measured by a method called equalibrium dialysis

I am not sure why your doctor ordered this blood test.

what is more important is what your TSH level is. T3 and T4 can vary and change, but your TSH level is a much better evaluation of your thyroid hormone status.

do you know what your TSH level is?
Customer: replied 10 months ago.


My TSH and T4 levels were fine. So if they were in the range, I do not need to be concerned about this T3 number? I have hypothyroid and hashimotos disease. My medicine constantly needs to be adjusted. My TSH is not the best guide for this. So, my doctor actually uses Free T4 and Free T3 to get the most information.

Expert:  Dr. David replied 10 months ago.
you don't need to be concerned about you T3 number

I would get a conventional T3 level instead of a equalibrium dialysis measurement of T3

that is good your T4 and TSH levels are normal.

most likely your T3 will be normal as well.
Customer: replied 10 months ago.


I appreciate your recommendation. It sounds like she accidently ordered the wrong test. However, now that I have an equalibrium dialysis measurement of T3 and it is out of the range, I will still be charged $45 by you for your response. I do not think that your answer of "you don't need to be concerned about you T3 number" is a detailed enough answer to warrant this amount of money. Please provide me more information regarding this type of thyroid test and what causes the thyroid to go below the normal range on this type of lab test. I am well educated and would like a detailed answer for this type of payment even if I have no reason to be concerned.

Expert:  Dr. David replied 10 months ago.

most circulating T3 is bound to plasma proteins, like thyroxine binding protein. only about 0.3% exists in the free, unbound state and is available for ex-change with intracellular T3 receptors.

when an increase in circulating thyroxine binding protein is suspected as the cause of an elevated total T3 level, the free T3 assay can differentiate this condition from true hyperthyroidism.

with a measurement of free T3 with equilibrium dialysis, radioimmunoassay (RIA), you also need a thyroxine binding protein level as well to understand the whole picture.

so your very very low free T3 level is normal since only about 0.3% of the total T3 is free.

does this make sense?

Customer: replied 10 months ago.


It makes sense in the way you described it. However, if that is the case, then why wouldn't the standard ranges be different to reflect this?

Expert:  Dr. David replied 10 months ago.
your thyroxine binding protein levels could be high which could be causing your free T3 levels to be low

so talk to your doctor about getting your thyroxine binding protein levels checked.
Customer: replied 10 months ago.


If my thyroxine binding protein levels were normal or low and my T3 levels were as I reported on these labs, is there any other information that you would you could provide based on that information.


 

Expert:  Dr. David replied 10 months ago.
no,

remember this is a measure of Free T3, which is different from T3.

T3 is the lab test which should be checked. Free T3 is only a very very small percentage of your T3 hormone.
Customer: replied 10 months ago.

So, just to summarize: If your free T3 is extremely low and your thyroxine binding protein levels are normal or low, there is no cause for concern. This is completely normal. This lab test showing that these free T3 scores are completely out of the range are unimportant and should be disregarded.


 


If this is true, can you please tell me in which case this test is supposed to intentionally be ordered and the results should be paid attention to.

Expert:  Dr. David replied 10 months ago.
when an increase in circulating thyroxine binding protein is suspected as the cause of an elevated total T3 level, then a free T3 assay can differentiate this condition from true hyperthyroidism.

say your T3 level is high, but your doctor thinks this is a wrong level and that you are really euthyroid (normal thyroid) and your doctor suspects that your thyroxine (T3) binding hormone is elevated and causing your T3 levels to be high, then a free T3 assay can be checked. if your thyroxine binding hormone is high, then your free T3 level will be low, and so therefore your doctor will say, they the high levels of thyroxine binding hormone is what is causing your T3 levels to be high, and then not to worry about the high T3 levels.
Dr. David, Board Certified Physician
Category: Medical
Satisfied Customers: 30111
Experience: Experienced Physician trained in New York City. I'm ready to help.
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