TT in 2013. Taking T3 only but T4 showing in b... - Thyroid UK

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TT in 2013. Taking T3 only but T4 showing in blood tests

France1 profile image

If I have no thyroid and have been on T3 only since September 17 - would you expect there to be any T4 in my blood tests?

Very confused about this.

12 Replies

I have not heard this before probably due to the fact other TT patients are not on T3 only. I wonder if the T3 picks up an iodine molecule if that's even possible. I'd love to know the answer to that. I wonder if it is in the testing procedure. What level of FT4 did you have?

Has your thyroid been deliberately burnt out with radio iodine or surgically removed? Otherwise, you cannot know if you still have a small remnant of working thyroid that might still be giving out a little T4. Otherwise if the T4 is almost but not quite zero, this number is a false one owing to test inaccuracy at these very low levels.

It is my understanding that taking T3 does not effect the TSH feedback loop at low levels, so the thyroid would continue to produce T4. May I ask what your dose of T3 is?

No thyroid all surgically removed 5 years ago.

I take 75 of T3 spread over a day. 37.5; 25; 12.5

Blood test before any meds taken

TSH 0.032 (0.360 - 3.740)

T4 FREE 1.23 (7.60 - 14.60)

T3 FREE 4.08 (2.18 - 3.98)

T4 should surely be zero


diogenes profile image
diogenes in reply to France1

This low FT4 value is an artefact. This is because the accuracy of the test so near 0 is not enough to prevent a false or very low number coming up purely at random. Testing again might easily give a negative number - clearly an artefact. Test values are always X + or - some percentage e.g. 14 +/- 0.5 This would be an imprecision of 0.5/14 or about 3 and a half %.

guysgrams profile image
guysgrams in reply to France1

WOW, I take T3 only (25 mcg twice daily) and still have my thyroid and my FT4 is 0.1 (.8-1.7) on my last lab. You would most certainly think there would be a reading less than what you have.

My recent tests just say <4 for t4 i was surprised my TSH was 2.1 i am also on 75mcg t3 only since june 2016 I had my tests done in france 4 weeks ago. I am waiting for my recent SHBG test as i still get very tired very easily, my last shbg was 58 which is low and shows low cell saturation should be between 70-90 for good t3 utilisation. So looks like i am due an increase as t3 not yet top of range.

If i take my t3 4-5 hours before test my t3 is top range it all depends when your last dose taken with t3, in france they like you to do early fasting test no meds.

I dont get too bothered by tests as it should be more about how we feel, do we feel good and same energy as any other person, for me the answer is no. I had a TT and i have never returned to the dynamic active person i was.

France1 profile image
France1 in reply to endomad

Shbg can you pls explain this to me. Thanks

endomad profile image
endomad in reply to France1

my nhs endo is well aware that we can tinker with test results by missing a few doses etc before tests with t3 to manipulate the test results, so he also does SHBG sex hormone binding gob something :) it is a chemical thing in liver and if good t3 saturation in cells it will be between 70-90 and we cant tinker with this test.

He has caught a few out with it being 90-120 and therefore over medicated but their t3 tests shows middle range, i will look up the explanation in min and post it.

At least my endo knows its about cellular saturation, not how much is sloshing around in your blood but how much your body is using x

endomad profile image
endomad in reply to endomad

here it is, lucky i keep all my thyroid stuff i have had to repost this so often xx

SHBG: Regulator and Indicator

The endocrine system, which encompasses hormone functioning, is known for its synchronicity. Yet factors such as stress, diet, pharmaceuticals, and environmental toxins can all disrupt hormonal balance. Because of its integral role as a hormone transporter, SHBG can be used as an indicator of how the system is functioning.

The role of SHBG is to protect regulate, and transport sex hormones, estrogen and testosterone. Produced primarily in the liver, SHBG binds to the hormones and shuttles them to tissues in body. When bound to SHBG the hormone, i.e. estrogen, it isn’t “free” or available. It’s important for the body to maintain the right amount of available estrogen, relative to the bound estrogen, as well as to the other hormones. Balance and synchronicity are key. An imbalance, along with low SHBG levels is frequently found in conditions with low thyroid transport (previously listed).

SHBG production responds to thyroid and estrogen hormones, which is why it’s considered to be a good indicator of thyroid tissue levels. In general it is a better marker for women than men. If estrogen levels are satisfactory, SHBG can act as a marker for tissue levels of T3 unless a woman is taking oral estrogen hormone replacement therapy (HRT). In this case, SHBG levels will elevate in response to increased estrogen levels in the liver caused by metabolizing the HRT. SHBG testing would therefore not be a true indicator, unless transdermal patches or creams are used. Simply put, SHBG levels impact estrogen and estrogen affects the thyroid. Thyroid hormones also affect SHBG levels by increasing its production and often diminishing free estrogen. Confused? Here is a gauge:

SHBG for women with adequate estrogen levels should be above 70 nmol/L, and men above 25 nmol/L. For those using thyroid replacement and are below these SHBG levels, it can signify ineffective treatment. SHBG levels are expected to increase when thyroid hormone medications are implemented.

If my t4 reading comes down to inaccuracy of testing then the doctor surely will not be able to be alarmist about the t3 being just over the range . That too may be inaccurate.

endomad profile image
endomad in reply to France1

i dont trust any of the tests after my TT my gp said my thyroid was still working perfectly well !!! as tsh was 5-6 in my ignorance back then, i accepted what he said and was slipping in and out of near coma, i couldnt stay awake more than an hour a day, so i have little faith in thyroid tests, the labs or the drs.

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