I’ve been reading here for a few years now and I think I’ve pretty much got to grips with how my thyroid works (or doesn’t in my case). But something has been going over and over in my crazy head.
What is it that TSH does? I mean if the TSH was non existent then does that mean the pituitary gland is not working at all? What happens to the body if the pituitary isn’t producing ANY TSH at all? Why to medics panic if the TSH goes below 0.04? If the thyroid hormones are added to the body “synthetically” what does it matter if the TSH is non existent 🤷♀️.
I’m waffling I know……. only one coffee so far this morning.
It’s the biology part I’m getting at. I understand the HPA and HPT axis and feedback loops but if the “P” in the loop is removed by medication what would be the problem?
Also how it that medics say “ under range TSH causes AF and osteoporosis”? What’s the biology/ physiology behind those beliefs?
I know that’s lots of questions 🙈. Please can answers be in simple terms for dummy’s like me.😊🤓
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SarahJane1471
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Indeed! What is the science behind these myths of osteoporosis & AF? It's not proven.... That's the truth. It's a myth perpetuate by ignorant professionals. Sadly none of them peddle the consequences of under or no treatment. Mores the pity!As for TSH. Primarily it's cheaper if they can just use TSH blood test result as a guide to treatment..... The science shows that treating by TSH alone leads to under treatment. But doctors these days are led by a chain to their noses.... They dare do no other than what the pathways say on their screens!!
What really counts is your actual thyroid hormone levels, your symptoms signs, how you feel and keeping certain mons bits optimum.
That is central hypothyroidism where the fault is with the pituitary gland and not the thyroid. It is characterised by low thyroid hormones and low tsh. Folks would be on replacement hormones as hypos.
TSH ('thyrotropin') stimulates the thyroid to secrete thyroid hormone. There is also evidence that TSH promotes T4 to T3 conversion although this is never stated by doctors (I've put the evidence here ibshypo.com/index.php/tsh-r... .
The secretion of TSH is regulated by feedforward and feedback mechanisms. The hypothalamus secretes TRH (thyrtropin releasing hormone) which stimulates the secretion of TSH. This is the feedforward mechanism. In rare cases of starvation or severe illness (e.g. heart attack or major burns) the hypothalamus may reduce TRH secretion.
Thyroid hormones feedback and suppress TSH. So, these two mechanisms ensure steady levels of fT3 and fT4 in healthy people (levels will vary but within individual limits).
Thus, in most cases TSH can be a marker for thyroid status. If the pituitary or hypothalamus fails TSH (and fT3, fT4) will be very low. If the thyroid fails TSH will go high as the pituitary detects low fT3, fT4 levels and secretes more TSH in an attempt to restore normal fT3, fT4 levels.
However, things can in some cases go wrong. The 'axis', the relationship between TSH, fT3, fT4 may be down-regulated by a long period of thyro-toxicity such as during hyperthyroidism. In this case TSH no longer reflects the status of fT3 and fT4. My view is that in these cases subnormal TSH levels lead to reduced T4 to T3 conversion in local tissues which is not fully reflected in blood hormone levels. An added complication is that TSH is a group of large molecules with varying bioactivity, the assay just measures how much TSH there is not its activity.
In summary, TSH is usually a good indicator of thyroid status and useful for monitoring hormone therapy. However, it is not always reliable and doctors tend to be in denial about the limitations of TSH.
If you don't get thyroid hormone tablets you die. Without TSH the thyroid will not secrete sufficient thyroid hormone to keep you alive for very long.
If TSH is zero because you are taking thyroid hormone you may be at increased cardiac and bone risk, this depends on whether your TSH is zero because you are taking too much hormone.
I’ve read your posts about the risks. I’m just curious to know “why” there is the risk. I.e what actually happens to the body when TSH is suppressed (with or without replacement hormones) that puts to you at risk of OA, heart, cancer? If you are supplementing the hormones your body needs, why is there a risk?
There is a reluctancy in making these claims because the research stating categorically that a suppressed TSH brings higher risk of impaired cardiac and bone health, in the presence of the correct amount and ratio of thyroid hormones, doesn't exist.
And in fact what we see on the forum time and again when all needs for good bone health are met is a reversal of poor BMD, just like we see raised cholesterol and liver enzymes lowering, GFR and kidney function raising, a jumpy and erratic heart beat levelling, gut motility improving, in other words everything re-normalising, and sometimes this happens with a low/suppressed TSH. NDT was the previous thyroid hormone replacement first offered and people seem to do well on T3-only, both which induce a lowered/suppressed TSH and we haven’t seen negative repercussions as of yet but that doesn’t mean there isn’t any.
TSH receptors are predominantly expressed in the thyroid glands thyrocytes, but also found in the pituitary, hypothalamus, adrenals, liver and kidney, adipose tissue, gut, heart and bones. It depends on how important its role is these areas and that remains unknown at this stage.
jimh111 so if you keep FT3 &FT4 within range it doesn’t really matter if TSH is suppressed because your body is getting what it needs 🤷♀️. Have I understood that correctly?
Not quite. fT3 and fT4 may be in their reference intervals but too high or two low. We each have an individual set point where our hormones naturally lie (with daily variations). If fT3 and fT4 are both high normal most people would be hyperthyroid and this would be reflected by a low TSH.
TSH is usually a good indicator of thyroid status, for healthy people and many thyroid patients. The problem is that sometimes TSH doesn't reflect thyroid status and doctors fail to realise this. When TSH is not reflecting thyroid status it is more difficult to determine what hormone levels a person should have, especially if they have more complex forms of hypothyroidism where individual tissues have different hormone status.
I mean if the TSH was non existent then does that mean the pituitary gland is not working at all?
No. It means that the pituitary is satisfied with the levels of thyroid hormone in the blood and considers that it's not necessary to stimulate the thyroid anymore. If the pituitary wasn't working at all, you'd be dead, because it produces a lot of other hormones apart from the TSH.
However, the pituitary can malfunction, just like the thyroid can, so TSH levels aren't always a reliable indication of thyroid status. Plus the fact, that when there are thyroid hormones in the blood, the pituitary gets served first, so to speak. So, the pituitary can be satisfied, but other parts of the body can still be low on thyroid hormone.
Also, the pituitary only goes by what is in the blood, It cannot indicate how much gets into the other cells. Nor does it actually know if you have a thyroid or are living on exogenous hormone. Plus there are so many external issues that can affect how much TSH it produces, like drinking coffee, having a fever, or even the time of day.
So, even apart from the myths, relying solely on the TSH is a very bad way of treating hypothyroidism.
so it REALLY doesn’t make sense why they use TSH as a marker at all!!!! And if we non medical people can see that why can’t the medics!!! It seems so illogical to me 🤷♀️.
Let’s say after years of PTSD my pituitary is struggling because it’s been messed up by my HPA and HPT axis going haywire. This should be so obvious to medical professionals that my TSH is not a reliable measure, because the H&P are not working properly, and my FT4 &FT3 levels should always be measured!!!!!!
😡this makes me so mad that even stupid people like me can understand
I doubt they've ever seriously thought about it. We have because our lives depend upon it, but they have no real idea what it's like to be hypo, for the most part. I don't understand why doctors that do have don't take more interest, but that's another story. I can only imagine that they go by what they were taught in med school. If they were taught it in med school it has to be right! And if they weren't taught it, it doesn't exist. That appears to be the mantra of most doctors. It's not lack of intellegence. It's not caring coupled with absolute faith in what they've been taught.
Medicine seems to be totally resistant to learning by lived experience!! If they listened and chose to learn from us who present in their surgery time after time with symptoms that don't go away we would all be so much better. Instead they look at the 80% who do well on t4 alone or who by some miracle manage to keep their tsh in range and be well and give themselves a big pat on the back! Success....it must be the patient who's wrong!
That's very true. But, they don't listen to us because we haven't been to med school. And if you haven't been to med school, you can't possibly know anything. I've actually had doctors tell me that!
You aren’t stupid, you understand it all far more than I do. I can read all the information, but does it stay inside my head? hardly at all. So if you are a dummy, then I am a dummy minus. x
I have had to TSH is the gold standard row with GPs and Endos a few times. Sometimes I challenge when they last read a paper on thyroid and then make one up, saying "thats not what Zeigler and Ulong said in their latest paper". I have never had one directly challenge me on this "research". This does show them that I can read, and am interested in the latest research, which they are not.
Sometimes I ask if they just go by the oil light in the car to make sure there is enough oil, but never book the car in for an oil change or test the oil filter or oil pump. Of course they rely on the oil light, but they usually see the point that something else in the whole process could be faulty. I have never had one say they check the dipstick!
All we can do is find out for ourselves, as you are doing, and then be our own doctors. Its is a crying shame that the medical profession just dont care.
My TSH level has always been incredibly low which is why I was not diagnosed for a very long time. However my levels of T3 and T4 were practically non-existent. I have Hashimoto's and have given up having my levels checked via the NHS. They won't check antibodies and are fixated on TSH levels. My GP agrees with me but because everything is computerised now, she cannot easily over right the system and specify the exact tests that should be done, unless cancer is suspected. I test privately through Medichecks now.
I function happily with TSH of 0.001. Have done for years, with and without added T3. Try and up it, can’t Ben iro a couple of t-shirts. But! AF and now a pacemaker so who knows. Bones bearing up nicely!!
Thankyou for your response. I don’t think I have AF. My heart rate is a steady 60. No palpitations or irregular beats. Blood pressure pretty low at 110/60. In fact since taking T3 it’s gone up from 95/59 which I think is healthier
if it reassures you at all SarahJane ~ my TSH has been relatively low since 2005.. i have no heart issues at all , not even a palpitation (no family history of heart issues)
2019 on 125mcg ~ 0.041 [0.57 -3.6] ..fT4 206% (i felt fine , but GP reduced to 112.5mcg)
2019 on 112.5mcg ~ 0.097 [0.57-3.6 ...fT4 242% (GP reduced to 100mcg)
2020 on 100mcg ~ 0.511 [0.57 -3.6] ... fT4 181% (i was now a constipated zombie so dose put back up to 112.5mcg)
2020 on 112.5mcg ~ 1.947 [0.57-3.6] ... fT4 142%
Still on 112.5mcg since then, but don't have reliable results and not particularly bothered about getting any at the moment as, frankly, my blood results don't seem to be very informative anyway. So at present i go mostly by symptoms, tweaking dose between 112.5 -125)
thanks tattybogle . Wow your results go all over the place ! I’m just anxious about my TSH being 0.02 BEFORE adding T3 which probably means it will go even lower. I haven’t done bloods yet as I’m still tweaking the T3.
If possible we would all like a 'risk free' looking TSH result..... but at the end of the day you have to be pragmatic .
What's the point of having a reassuring looking 10 year TSH history , if you have been a sofa sloth for those 10 yrs ... and if a 'risky' looking TSH gives you a quality of life that is closer to 'human' than 'sloth'..... would you pick 'sloth' to minimise the risk .. probably not.
if you were largely sofa bound and out of work with no social life and a GP said i can give you this new drug to make you better , but it comes with a 5% risk of getting AF.... would you take it anyway ? ... probably.
well said 👏. Thank you. It’s so bloody obvious when you put it like that 😂. I have been exactly that ….. a sloth for 4 years. I want my life back. I think I’m trying to run before I can walk and expecting my body to have caught up after only 2 months of adding T3 to Levo. I’m still crashing after exertion. But I’m forgetting how shite i actually felt before.
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Question as to if i can not tolerate Levothyroxine
Why measure TSH when you have no thyroid.
Little off topic, a question on a survey...
I am new here and would appreciate a little advice. 
A little explanation please
