I hope this isn't annoying as I am still trying to learn this and understand better.
I understand that for 90% of people with hypothyroidism TSH is a good indicator to use for fine tuning their medication dosage.
But then there are the other 10% who can have various other issues getting in the way of getting that correct dosage.
I am in tbe situation where my TSH is normal but my symptoms never went away (only a minor improvement). So, I have been stuck on 50 levothyroxine with my doctor unable to change the dose and the lab refusing to do a t4 test. (Making that my new crusade and have put in some complaints that the dr can't even request the correct tests according to NICE guidelines as the lab vetos it).
I have a medichecks test booked for Monday to do tsh/t4/t3 as I have been convinced this could give me answers.
Now... Could you please elaborate on how it works that tsh can be normal but t4 might possibly be low (and t3 too, I guess, but one thing at a time).
Sorry, I forget the name, but someone showed me their own results that showed their tsh didn't exactly change drastically as their levothyroxine was continued to be adjusted.
I guess I am still not understanding how tsh and t4 work when tsh is normal but t4 is low. My brain wants there to be sine logical correlation but seems like maybe there isn't?
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Hi I'm no expert but I know that TSH is made in the pituitary following the stimulus of TRF. So if there's something wrong in the pituitary then TSH production will be messed up. I think they call that secondary hypothyroidism.
I did an article talking about a sort of spectrum of pituitary dysfunction to disease... I know very little but seems this isn't even something considered by a GP.
The official diagnosis of a faulty pituitary function where TSH and FT4 levels do not collaborate is called central or secondary hypothyroidism.
However, there are many of us (possibly the majority of hypo forum users) whose TSH fails to match their FT4 levels, thought to due to a down regulation of signalling. This could be a result of year of inadequate thyroid hormone levels making all systems struggle.
There is also those who can not achieve wellbeing on T4 mono therapy no matter how high FT4 levels are taken because they simply can not convert enough T3. These people have to medicate a little T3 and this is likely to lower TSH also.
I would say it is more than 10% of hypo sufferers who have a low TSH, of which many are kept under medicated and unwell, some have T3 prescribed and others self medicate T3. Whatever scenario a low TSH is usually frowned upon, and it is not true it alone causes bone health and heart issues.
TSH is produced in the anterior pituitary in response to both Thyrotropin Releasing Hormone (from the hypothalamus) and the blood thyroid hormone content.
Within the pituitary, the T4 content of the blood is converted into T3 and any actual T3 in the blood combine to adjust the amount of TSH produced.
Anything going wrong can result in an inappropriate level of TSH being produced.
E.g.:
Insufficient TRH produced by the hypothalamus
Inadequate ability of the anterior pituitary to produce TSH. (In severe hypothyroidism, the pituitary can grow - in order to produce more TSH. But if the pituitary is small, or in some way impaired, it might not be able to make more TSH.
But once you are within the brain things can be very different as much of the T3 used by the brain is converted locally, within the brain, into T3. And even that is far more complicated than I know about!
I understand that for 90% of people with hypothyroidism TSH is a good indicator to use for fine tuning their medication dosage.
That's a very generous estimate. I would have said 0%! The TSH test was devised as a diagnosis tool, not to dose by. And even then it's not that reliable, for reasons explained by others.
And, once it gets below 1 it becomes even more unreliable because it cannot go below zero. So, you have have someone with an FT4 of 70% through the range and the TSH is 0.01, and someone else with an FT4 of 102% and the TSH is still 0.01. And whilst the person with an FT4 of 102% needs his levo reducing, the person with only 70% probably doesn't. To a GP, it's all the same.
Now... Could you please elaborate on how it works that tsh can be normal but t4 might possibly be low (and t3 too, I guess, but one thing at a time).
Depends on your definition of 'normal'. If you just mean somewhere - anywhere - within the range, then that is wrong. The range is too wide. And a truly 'normal' (euthyroid) TSH is around 1. But even 1 would be too high for a lot of hypos because they need their Thyroid hormone levels higher than euthyroid (i.e. around mid-range) and therefore the TSH a lot lower.
Plus, a lot of things can affect the TSH level - most importantly, the time of day! A TSH of 1 would be a lot higher before 9 am. And there are things that can affect the analysis of the blood, like anti-TSH antibodies that can cause a TSH level higher than it should be.
And, dosing by the TSH is assuming that everyone's pituitary always works perfectly. And it doesn't. Anymore that everyone's thyroid always works perfectly.
And the TSH doesn't distinguish between the T4 and the T3, so you might have a high T4 and a low T3 because you are a poor converter, and the TSH doesn't always reflect that. So, dosing by the TSH is fraught with hazard!
My brain wants there to be sine logical correlation but seems like maybe there isn't?
That's what doctors want, too. But there isn't one, so they invent it. They are not taught how to interpret blood test results, with all the intricacies, so just looking at the TSH makes it easier for them, and the patient suffers... Could go on, but I won't!
I like learning all of this... But I also wonder how I will ever get the right treatment with all that to contend with... Plus the nhs.
I also don't fully understand how the autoimmune aspect plays in. One camp says hashimoto's has its own symptoms and dealing with inflammation will give your body less stress to tackle the antibodies.... Then the other just says when hypothyroidism is appropriately treated you'lm not have any more symptoms.
I don't kniw how to get my head around everything starting with T and the factor in the autoimmune side to have a realistic expectation.
In my view, the only way we can possibly reach widespread decent treatment is through technology.
There are computer models of thyroid function. They are being developed and tested. We are seeing papers which check how well models correlate with each other and with actual human bodies.
They can easily outperform most doctors - especially non-specialists.
But implementing such systems requires a lot of changes. Things like far more testing of the computer models. Comprehensive and frequent testing of the subjects. Dosing with finely graduated doses of at least T4 and T3.
We also need to look at other computerisation histories - and I think aircraft provide a lot of lessons. Things like suddenly finding major holes in the systems. Many aircraft survived because experienced pilots were able to identify system issues and override them.
My TSH and T4 were in the ‘normal ranges’ but my symptoms continued. I have the DI02 genetic mutation (discovered after following discussions and links on this forum) so don’t fully convert T4 to T3. I now buy T3 online and self test to make sure my levels are ‘normal’, except for the TSH which is suppressed because, I assume, my body has sufficient T4 and T3 and my thyroid system doesn’t need stimulating by the TSH. PM me if you want.
Blue Horizon offer the test. I used Regenerus Laboratories but they no longer offer it. You may not have the mutation but, for me, it was worth finding out.
Hopefully you have your test before 9 fasting, drinking only water and leaving a gap of 24 hours between your last dose of levo? If you dont do this it will cause a low TSH. Also best to keepcto the same time each time for comparison.
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Update: GP Reducing Levo - TSH Low / T4 / T3 in range
TSH and T4 levels
Recent Lab Results: TSH improves, T4 and T3 at standstill. 
Feedback loop TSH/T4/T3
