I was just musing, (it’s Sat, raining and cold and I have nothing else to do!), over a really detailed and helpful answer MaisieGray had given about T3 and T4 to a poster.
I know there are %s we can look up about how much T3 a healthy thyroid might secrete and what makes a healthy conversion ratio, though of course, how we feel should always be the bottom line. As we know, normal ranges can damn us all to under-medication, so I wondered if there may be some of us who don’t necessarily have a conversion problem but had a thyroid that used to naturally produce more T3 than might be considered normal and less T4 and that’s why we struggle?
If that was our ‘normal’, even if we convert T4 reasonably well, it won’t ever be enough. Or would a working thyroid doing that just make you hyper? Maybe not if it had lowered T4 secretions?
But then again - that would be judging on a blood test - and if you didn’t feel or have the symptoms of hyper - we would probably argue you aren’t. I was always on the energetic side, naturally skinny, a bit highly strung and very lively before I got hit by the brick of this illness. I thrived on stress and work. Could it have been that higher than normal T3 was my individual normal state? I wonder if anyone else had any thoughts on this? Hope this makes sense, and by all means tell me if I’m talking b*ll*cks! 🤸🏿♀️
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MissGrace
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I liked your cartoon very much. It is amusing but truthful.
As your question might not be answered by a Professional, these are two excerpts and it is good to ask questions as few doctors or endocrinologists would seem to know the answer, I believe.
"Thyroxine (T4) and triiodothyronine (T3) are important hormones produced by the thyroid gland that are essential for brain and physical development in infants and for metabolic activity in adults.1 Thyroid hormones help the brain, heart, liver, muscles, and other organs function properly.2 If unregulated, thyroid hormone imbalances can lead to life-threatening conditions such as myxedema coma (dangerously low thyroid hormones) and thyroid storm (excessive thyroid hormone concentration). Health care professionals should know how to monitor these hormones to prevent emergencies and improve outcomes." and
"Let’s review thyroid hormone production.
The thyroid gland, located in the anterior neck, consists of two types of cells: follicular cells, which produce T3 and T4, and parafollicular cells, which produce and secrete thyrocalcitonin (also called calcitonin).3 The thyroid takes iodine, found in our diet, combines it with an amino acid, tyrosine, and converts it into T3 (containing three iodine atoms) and T4 (containing four iodine atoms). T4 is produced solely by the thyroid gland. About 80% of T3 is formed by the removal of one iodine atom from T4, a process called deiodination. This occurs primarily in the liver and kidney, but T3 is also produced in some, if not all tissues.1 Factors that inhibit the conversion of T4 to T3 include stress, starvation, beta-blockers, amiodarone, corticosteroids, iodinated contrast media, and propylthiouracil (PTU).3 Cold temperatures may increase the conversion.3 The thyroid gland synthesizes and stores mass quantities of T3 and T4 within the protein thyroglobulin.1
T3 and T4 production is regulated by thyroid stimulating hormone (TSH) secreted by the pituitary gland, which is in turn regulated by thyrotropin-releasing hormone (TRH) secreted by the hypothalamus.2 This process works as a negative feedback loop. When levels of T3 and T4 decrease below normal, the pituitary gland produces TSH, stimulating the thyroid gland to produce more hormones and raise the blood levels. Once the levels rise, the pituitary then decreases TSH production.
I do think it might mean - as it would if someone had not good but okay conversion, that we may need T4 above the normal range if we are on monotherapy. My specialist did say to me that (as we know) hypo patients need to be at the top of the normal ranges for the simple reason they are not normal. Makes me think some need to be above the normal ranges - for the same reason. And that would include for T3. I have a feeling he would be okay with me on T4 slightly above normal, but might get a bit wobbly if the T3 was! As I’m still increasing Levo because my T3 only moves up so slowly with each increase, we’ll see! #willingtobeaguineapig - want to feel well!!! 🤸🏿♀️
I've no answers I'm afraid, but a couple of points: You're assuming that people whose levels naturally run high or low within the reference ranges are thereby normal, but might it be the case that that is nevertheless not healthy, or not optimally healthy for them ie what normally happens is not necessarily what should happen. For instance, a previous Prof Endo of mine carried out research to look at individual response to consuming calories, and (unsurprisingly to me at least) proved that "if you give a 1000 people the same number of calories to consume, some will gain weight, some will lose weight, and some will remain the same weight". So their individual response would certainly be "normal" to them, but not necessarily optimal, healthy, or safe; or even arrived at from the same aspects of functioning. Then, that you "thrived on stress and work" may have been the case psychologically, but not necessarily physically, and may even have been having a deleterious effect on your physical health. There certainly can be psychological drivers to that type of behaviour, whether innate, learnt or externally imposed; and also addictive-type behaviours such as that seen in the proverbial adrenaline-junky types; which again may or may not be normal for them but may definitely be unhealthy. I guess the parallel is saying that some ingested stuffs must be safe because they are natural, but natural doesn't necessarily equate to safe. My parents were hard workers and psychologically well balanced, but my father was 6 ft and weighed only 9 stone 8 lbs (even though he had extreme upper body muscle from hard work), which I suspect was as a result of the starvation and general deprivation he experienced as a prisoner of war, returning home weighing only slightly over 5 stone and suffering intermittent lifetime bouts of the effects of dysentery - so it was his "normal" for the majority of his life post WWII, but unlikely to have been his innate normal. I therefore probably both inherited, and learned (nature:nurture) the hard work ethic and the not-be-stressed response; so you seeking out and thriving on stress and hard work would likely have a different effect than me doing the hard work without the stress aspect. Additionally, attitude/personality can play a large part in how little or much, an illness or indeed any other event, can affect us and how we experience it. Sorry, that's a long way round to say I don't know, but be careful of assumptions and generalisations ... 😉
Interesting isn’t it? Because who would judge if it is healthy or safe for that individual particularly if they feel fine and have no symptoms of malfunction? I’m not talking about anyone who is ill or whose body is misbehaving. That brings us full circle back to judging on blood tests not symptoms which isn’t good enough.
I realise there are many factors involved, but that again brings us back to the big issues with the way our blood tests seem to simply trump our symptoms with so many GPs and endos.
I thrived on work and stress both mentally and physically and was completely physically healthy until becoming hypo. I don’t get coughs, colds, flu, never had a sickness bug in my life etc. I exercised a lot - I can’t do quite so much now - and I know that helped keep me healthy and because I had a good level of fitness that has helped me since becoming ill. Thanks for the response. 🤸🏿♀️
Abdalla, S. M., & Bianco, A. C. (2014). Defending plasma T3 is a biological priority. Clinical Endocrinology, 81(5), 633–641. doi.org/10.1111/cen.12538 (doi.org/10.1111/cen.12538)
Hashihouseman posted this paper to me, which from my recollection included some detail on this.
I’d like to say yes I did - but that would be a nose-growing fib! I found it on the internet. By all means share. It hits the nail on the head doesn’t it? 🤸🏿♀️
I'll try and work this out - I can only express the answer as an average, because the numbers will be slightly different for each person. There is about 1.6 mmol/L of T3 in the healthy body, almost all in the bloodstream. There is about 100 mmol/L T4 similarly. So the ratio of T4/T3 (totals) is about 60/1. Of the T3, 80% was converted in the body from T4, which comes out at 80% of 1.6 = 1.3 about. So the remaining 0.3 mmol/L must come direct from the thyroid. So the thyroid must be on average producing about 300 times more T4 than T3. We can ignore T4-T3 conversion in its effects on the T4 level, because it is very small compared with the huge T4 reservoir.
You're saying the ratio of T4/T3 is about 60/1. The numbers I've read were 15/1 or 10/1 production from the thyroid gland. Can you explain the huge disparity?
Are you saying an average thyroid gland produces 100 mcg T4 and only 1.6 mcg T3? If not, how does mmol/L translate to mcg?
I've calculated from frst principles knowing the average amount of T4 (total) and T3 (total) in the healthy body. These come from knowing the reference range for each parameter. BTW I should have said their concentrations are in nmol/l not mmol/L. This ratio is 60/1. So T3 production cannot be larger than that. Some of the T3 in the body comes from conversion in the cells (the larger part). This has negligible effects on the much greater Total T4 reservoir in blood which can supply the whole body for 1 week.
So if 80% is conversion, 20% is direct T3 supply. I don't know how others have come to their conclusions. There will be a further effect of the long lifetime of T4 compared with T3, but I wouldn't think it very serious, because the most of the T3 is conversion-led.
SewinMin - that is interesting and leads to another question of which I have no clue of the answer to - (though Diogenes might) - if the body can produce rt3, how does anyone ever become hyper or over-medicated on T4? Logically, the body just wouldn’t convert what it didn’t need or would convert to rt3 so it was inactive. Does someone go hyper when their thyroid overloads the T3? Or could it be if the levels of T4 are too high, the body can’t convert it to rt3 fast enough, or that some other aspect of metabolism/enzyme activity is breaking down?
What all these questions show is what a complex process thyroid/metabolism in and how finely balanced. So those GPs who say our issues are simply treated with T4 need a wake up call. All of these factors are coming into play for all of us as individuals.
Interesting, and perhaps important to those of us whose TSH is "Too low" and they want to decrease our Levo without even testing the T3! Which happened to me a few days ago. The Pharmacist may be correct that my apparent hypo symptoms are actually caused by overmedication (as when taking painkillers too often actually gives you a headache).
I follow her reasoning and it does make sense, so going along with it for now if only to prove or disprove the hypothesis. But when I asked if they ever tested T3 I got a firm "No".
Thankfully the decrease is only half of the usual 25mcg (from 100 every day to 100 and 75 on alternate days)
See how you go. In my experience the symptoms of being over-medicated were quite different to being hypo in lots of interesting and at times, scary ways. It’s not an experience I wish to repeat. But I am also continuing to increase despite my TSH being very low, under the guidance of an endo. And we both know I’m not over-medicated as I have no signs of being so. If I was, I’d stop immediately and pull back. 🤸🏿♀️
I have no obvious signs of being overmedicated (such as fast heartbeat or shaky hands), but she was adamant. And the only way to know who is right is to follow instructions. Also I messed around with my supplements during the last few months, and even fasted (had soup or drinks only) for several days (I had no idea that would upset things re the thyroid). So have to give this a fair chance, even for my own sake
Today I took an extra dose of t3 (5mcg on top of 10 mcg t3 as well as 88 mcg Synthroid or t4), to see how I will feel. So far I dont feel any bad effects. How long would it take to feel the negative effects after taking t3 and what symptoms to go by when deciding whether it is a good desicion or not?
what would be the signs of overmedicating? I am so confused as hypo and hyper symptoms are similar. Hair loss can be both hyper and hypo, fatigue can also, anxiety, weight loss. I have heard some people get high pulse rate with both hypo and hyper. My blood tests show that for both my t4 and t3 levels are below average and far from optimal, but when I would like to go by symptoms I don't know what to do because of this. How-to distinguish whether to decrease or increase the meds? My doctor thinks I am fine and since my blood levels show that I am not optimal (followed by not feelimg 100 percent) I dont want to decrease but he think I could do with a decrease. But he is going by the TSH so I dont trust him. 😭😤😕
For me, the first signs I had were a slightly sick feeling - like a syrupy sweet feeling. Then, if I just got up to make a cup of tea, my heart would race - literally. It would suddenly be at 120bpms. Even resting it was higher (normal for me was 56-66bpm) suddenly it was up to 80 at rest. I had to lay very still to stop it from suddenly racing and it was scary. I’ve never experienced anything like it before and it gave me new respect for what potent drugs thyroid meds are. The heart speeding up when I moved was the real sign. Watch out for fast palpitations, they can lead to AFib. I did lose more hair - that was noticeable too.
If you are over-medicated, I do believe from my experience you will know and detect it. I was over on T4, which stays in the system longer and despite reducing the symptoms continued (though not as severe.) I ended up having to come off Levo for 6 weeks and start again from scratch, very slowly, as my heart is now sensitised to it. T3 is out of your system in 24 hours I think, so if you over-medicated on it at least you’ll be out of the roller-coaster ride more quickly.
My blood tests at the time clearly showed my T4 and T3 over-range.
What I don't get is why they never seem to check heart rate, temperature etc any more. Though temperature wouldn't be reliable as I get hot flushes which seem to have become more intense since being on Levo.
Might that mean that peripheral organs such as skin get more T3 than for example the brain??? Interesting, I love finding things out. As a small child I once asked my mother "How is a crocodile made?" (Fascinating things, crocodiles, how they are put together must be amazing!) I was astonished when my mother said she didn't know!
Do you know what else is odd. If a normal thyroid produces T4 and T3, whatever the ratios, if we are only treated with T4, then surely we’d need more than the normal range to compensate for having no T3. And having more would really lower the TSH... 🤸🏿♀️
In a healthy person, much of the T3 used by the brain is actually converted within the brain. That is, T4 is transported across the blood-brain barrier (BBB) and then converted.
(That is not to say that no T3 is transported across the BBB.)
I really do not know how much T3 is used by different organs. However, I suspect that some such as Brown Adipose Tissue (brown fat cells) and Gastric Parietal Cells require more than some others. (This is only my guess.)
In a nutshell, the thyroid doesn't secrete 20% T3 and 80% T4, that is an AVERAGE which is meaningless given the wide spread of the individual results making up the data.
In this study, T3 secretion by the thyroid ranged from 6.5% T3 from the thyroid gland to 42%.
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