Aa
Free T3 way below normal, but normal TSH?
Just had labs done for a myriad of symptoms (rising diastolic blood pressure, severe sensitivity to cold, cold chills when it is warm, severe anxiety etc...)
My doc had suspected Thyroid problems before this but every time TSH would come back normal. It was by mere curiosity she ordered the free T3.
Here are my lab results and corresponding ranges.
Free T3
My value: <0.5 pg/mL
Standard Range: 2.8 - 5.3 pg/mL
TSH ultrasensitive
My value 2.020 mIU/L
Standard Range .465 - 4.680 mIU/L
I will hopefully understand more when I talk to the doc on Mon... but can anyone shed light on why my free T3 is so low but my TSH is within normal range? I'm not sure if this means my thyroid is or isn't functioning properly...
My doc had suspected Thyroid problems before this but every time TSH would come back normal. It was by mere curiosity she ordered the free T3.
Here are my lab results and corresponding ranges.
Free T3
My value: <0.5 pg/mL
Standard Range: 2.8 - 5.3 pg/mL
TSH ultrasensitive
My value 2.020 mIU/L
Standard Range .465 - 4.680 mIU/L
I will hopefully understand more when I talk to the doc on Mon... but can anyone shed light on why my free T3 is so low but my TSH is within normal range? I'm not sure if this means my thyroid is or isn't functioning properly...
COMMUNITY LEADER
It's impossible to know what's going on without the Free T4 test. Some medications can affect conversion, but without enough Free T4, there's nothing to convert.
I'm not sure where you got the information about metoprolol and gabapentin. If you have a link to the article(s), I'd like to see them because that's new information for me. I was on gabapentin for quite some time (years) and none of my doctors ever worried about conversion, nor did I have a problem with it, other than my usual conversion issue for which I take T3 medication. We did not have to adjust my dosages to accommodate the gabapentin. Of course, we're all different. I'd look forward to seeing those articles or knowing where you found them.
You can always discuss this with your doctor.
I'm not sure where you got the information about metoprolol and gabapentin. If you have a link to the article(s), I'd like to see them because that's new information for me. I was on gabapentin for quite some time (years) and none of my doctors ever worried about conversion, nor did I have a problem with it, other than my usual conversion issue for which I take T3 medication. We did not have to adjust my dosages to accommodate the gabapentin. Of course, we're all different. I'd look forward to seeing those articles or knowing where you found them.
You can always discuss this with your doctor.
4 Comments
Here is one of the links https://www.restartmed.com/low-t3/ "Medications can also reduce the conversion of T4 to T3 including: blood pressure medications, diabetic medications, pain blocking medications, anti depressants and nerve modulators (gabapentin & lyrica, etc.)."
I'm not a fan of Dr Childs but thank you.
Oh. Ok. Well, until yesterday I basically knew nothing about thyroid-related hormones etc...it was just one of the articles I came across. I'm sure you know much more than I do. It's comforting to hear you didn't have to adjust for your Gabapentin. Probably be best to do some further testing to figure out what's going on with me. The info I have received here has been very helpful so thank you
I'm not saying that your medication doesn't have "anything" to do with your problem because there are some medications that can cause hypothyroidism. Lithium, Amioradine, and interferon are the most common and as you read, others can affect the thyroid in various ways.
I'm very surprised your doctor would have tested Free T3 and not tested Free T4 because you can't really tell anything with just Free T3. If she'd been testing only TSH for a while, then threw in Free T3 on a whim, that makes me wonder about her thyroid knowledge in general.
When you get further testing, be sure she tests Free T4 and Free T3 in the same blood draw in order to get the proper comparison. She also needs to order thyroid antibodies to rule out Hashimoto's, which is an autoimmune condition in which the body sees the thyroid as foreign and develops antibodies to destroy it. As I noted previously, typically, we'd expect your TSH to be higher with Free T3 as low as it is, except in the case of Central/Secondary hypothyroidism, so you'll need pituitary testing as well. That would be the tests mentions by Red_Star above.
There are also some vitamin/minerals that can affect thyroid hormone production/conversion. Those include iron (get ferritin, which is the iron storage hormone, tested), vitamin D, vitamin B-12. Selenium is also necessary for the conversion of Free T4 to Free T3, but that's not, typically, tested on a routine basis. Once all your testing is done, you can probably just start taking that and see if it helps.
Cortisol is another hormone that can affect thyroid function and/or Free T4 to Free T3 conversion, so there are a lot of things that can be checked, but of course, getting that initial Free T4/Free T3 test will be the most important.
Your doctor has her work cut out; I hope she does it well.
I'm very surprised your doctor would have tested Free T3 and not tested Free T4 because you can't really tell anything with just Free T3. If she'd been testing only TSH for a while, then threw in Free T3 on a whim, that makes me wonder about her thyroid knowledge in general.
When you get further testing, be sure she tests Free T4 and Free T3 in the same blood draw in order to get the proper comparison. She also needs to order thyroid antibodies to rule out Hashimoto's, which is an autoimmune condition in which the body sees the thyroid as foreign and develops antibodies to destroy it. As I noted previously, typically, we'd expect your TSH to be higher with Free T3 as low as it is, except in the case of Central/Secondary hypothyroidism, so you'll need pituitary testing as well. That would be the tests mentions by Red_Star above.
There are also some vitamin/minerals that can affect thyroid hormone production/conversion. Those include iron (get ferritin, which is the iron storage hormone, tested), vitamin D, vitamin B-12. Selenium is also necessary for the conversion of Free T4 to Free T3, but that's not, typically, tested on a routine basis. Once all your testing is done, you can probably just start taking that and see if it helps.
Cortisol is another hormone that can affect thyroid function and/or Free T4 to Free T3 conversion, so there are a lot of things that can be checked, but of course, getting that initial Free T4/Free T3 test will be the most important.
Your doctor has her work cut out; I hope she does it well.
COMMUNITY LEADER
Was there a Free T4 test ordered as well? If so, what was the result?
With Free T3 as low as yours, we'd expect TSH to be higher than yours. Since it's so low, I'd suspect that you might have Central or Secondary hypothyroidism. With Secondary hypothyroidism, the thyroid actually works fine, but there's a problem with the pituitary gland in which it doesn't produce enough TSH to stimulate the thyroid to produce enough thyroid hormones. It's still hypothyroidism and has to be treated with replacement hormones.
Hopefully, she will get you started on medication as soon as possible. Since this is possibly a pituitary issue, it would be a good idea to have other pituitary hormones tested as well in case other imbalances could be contributing to your symptoms.
With Free T3 as low as yours, we'd expect TSH to be higher than yours. Since it's so low, I'd suspect that you might have Central or Secondary hypothyroidism. With Secondary hypothyroidism, the thyroid actually works fine, but there's a problem with the pituitary gland in which it doesn't produce enough TSH to stimulate the thyroid to produce enough thyroid hormones. It's still hypothyroidism and has to be treated with replacement hormones.
Hopefully, she will get you started on medication as soon as possible. Since this is possibly a pituitary issue, it would be a good idea to have other pituitary hormones tested as well in case other imbalances could be contributing to your symptoms.
1 Comments
Thank you for responding! She did not order the free T4 that I can see. Perhaps she will now that the Free T3 came back so low. I have been doing some research and I am wondering now if my medications aren't causing this. I have been on a beta blocker (metoprolol) for about 8 years now and I also take Gabapentin to level out my moods. I have read that both of these meds can interfere with conversion of T4 to T3.
Excerpt from Best Practice - Thyroid Function Testing:
"Normal TSH - associated with a low FT4 and/or FT3
These results may occur following secondary (central) hypothyroidism, which is associated with pituitary or hypothalamic dysfunction. TSH can be low, normal, or slightly elevated. Evaluation for deficiencies in other pituitary hormones should be obtained before imaging (i.e., pituitary MRI). Hormone tests should include: ACTH with cortisol, FSH, LH, oestradiol (female), testosterone (male), prolactin, GH, and (insulin-like growth factor 1 (IGF1). For this condition, thyroid replacement therapy is monitored by checking the levels of FT4 and FT3. [23]
Other causes include drug use (e.g., phenytoin, rifampicin [rifampin], carbamazepine, barbiturates) and assay error when interfering substances are present."
"Normal TSH - associated with a low FT4 and/or FT3
These results may occur following secondary (central) hypothyroidism, which is associated with pituitary or hypothalamic dysfunction. TSH can be low, normal, or slightly elevated. Evaluation for deficiencies in other pituitary hormones should be obtained before imaging (i.e., pituitary MRI). Hormone tests should include: ACTH with cortisol, FSH, LH, oestradiol (female), testosterone (male), prolactin, GH, and (insulin-like growth factor 1 (IGF1). For this condition, thyroid replacement therapy is monitored by checking the levels of FT4 and FT3. [23]
Other causes include drug use (e.g., phenytoin, rifampicin [rifampin], carbamazepine, barbiturates) and assay error when interfering substances are present."
1 Comments
Very helpful! Thank you! She did order an Estradiol. My value was 77 pg/mL during luteal phase (Standard Range 33-201 pg/mL ) so that was within normal range. I will ask about the others.
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