Some of my friends take T3 and not T4 (thyroxine). They say it is more biologically active and makes them feel better. Why am I not prescribed T3?
Although both T4 and T3 are thyroid hormones produced in our bodies, they have different properties. T4 has a longer half life and is converted into T3 in our blood and different tissues. The way our thyroid normally achieves appropriate levels of thyroid hormone is to secrete predominantly T4, and this is converted gradually to T3, as needed, in a regulated manner. T3 is more biologically active but can also rapidly increase heart rate and blood pressure and hence can be dangerous in certain patients, especially older patients or patients with one or more risk factors for heart disease. There is active interest in combining small amounts of T3 with T4 to see if patients feel better, and scientific investigation of these experimental treatment options is underway. For more information, see the section on Optimal Thyroid Hormone Replacement.
Written by
marymerry83
To view profiles and participate in discussions please or .
My endo, unfortunately, is a T4 only endo for exactly the facts above. He say's T3 can be to harsh on the heart and gives it an instant hit of thyroid hormone which can cause troubles (which it did in my case). But although it caused me heart troubles and I had to stop taking it I still miss the "wellness" it gave me. All the nagging remaining hypo symptoms like gum infections, sinus troubles, eyesight troubles and my ringing in the ears disappeard but when these were mentioned to my endo he dismissed these as non thyroid symptoms, which I know to be untrue.
I think if your body can tolerate T3 then all good and well but it needs to be overseen by a doctor wherever possible. My endo was also against NDT but I have no personal experience of this so couldn't fight the cause but I do not agree with his T4 is the best thyroid treatment available theory - its the cheapest but I dont feel its the best.
I know and agree, but without a heart nothing works. I think they could use t3 in small doses anyway. You are right in saying the treatment they use is the cheapest and unless you have the funds of a wealthy person, this is what you get. It is really sad how our social system works, but that is how they roll!!!!
Your endo is wrong!! T3 is NOT hard on the heart if you do not convert well then that IS hard on your heart!! If this was not so then why are heart specialists able to prescribe T3 to do rapid repairs when a person has had heart surgery? Being ill from hypothyroid is very hard on the heart and the body!!
I have been on T4/T3 combo for 3 months and never once have I had raised heart rate or blood pressure and I am 70. I am on 15mcg T3, which isn't a huge amount but its enough to make a difference.
Was rushing out so no time to say I am on T4/T3, am 75 years old, take 15mcg T3 in total daily, 5mcg x 3 times daily, so there is a constant flow of T3 but take it about 30 mins after food to slow down absorption so avoiding a "hit". In 1980 had ventricular tachycardia, told was result of max stress causing adrenaline blasts, took two years to get fighting fit again, a prime candidate for T4 only? when diagnosed hypo 2003, but now flourishing on T3/T4.
I'd have to say that I don't experience any instability on T3 - even now that I'm up to 40mcg daily spilt in two equal lots. With only 50mcg of T4. Even if at times I'm not the best at getting the timing of the two doses exactly right.
I've never seen it discussed anywhere, and this isn't to say that it can't produce some sort of rush at certain doses for some people - but there seems to me to be some sort of buffering effect even with T3 - especially after a few weeks when the system has got used to it. Taking quite a lot of my dose close together doesn't seem to produce any corresponding bump in blood pressure, heart rate and the like - at least not that I've picked up.
Wonder what the physiology of it all is?
Not sure if i have it right, but doesn't T3 also bind to proteins and circulate in the blood as total T3?
What I did see for a while ( acouple of weeks maybe?) initially was a tailing off a few hours after taking a dose. One possible explanation for that might have been that it takes a while for the total/bound T3 level to build up enough in the blood so that there is a reserve/buffer stock?
Meaning that whatever processes determine the rate of conversion and use of T3 (which I seem to recall is separate from the T4/TSH control loop, and maybe (?) involves the pituitary) in the cells must surely intervene?
i.e blood level of T3 doesn't directly/exclusively control the rate of the various metabolic processes that use it. Or does it?
Sorry Mary - it wasn't my intention to try to put you on the spot - it was intended more as a rhetorical question.
Nostone's link seems like a useful one - it sets out the picture in very understandable terms. I tend to agree with that Doc as I find that I feel better if taking at least some T3....
Thanks mm for the extract - do you have the source?
I seem to remember Dr Lowe mentioning the 'kick-start' effects of thyroid treatment - like being aware of heart beat/racing/palpations etc. ? so Levo T4 is 'preferred' as safer as T3 is perceived to be 'too strong' (if considered at all). However we see palps etc. symptoms not only reported by hyperT but also hypoT sufferers. But I notice folks seem to do well on the 'more costly' T3 or combo.
Personally, being an untreated hypoT with half a thyroid, I'd be too spooked to try T3 with my existing 'hyper' symptoms and without a good GP/Endo! (I did try NutriT but the palps got worse, so just eliminating deficiencies). J
the web site is Mythyroid.com. I am spooked about it myself. I let my situation of subclinical thyroid go without treatment for about eight years. Then several months ago my t4 was low and I had an extreme tsh of 94. I hate this but I guess it could be worse. Hope this helps.
The Wilson Temperature Sydrome protocol does low dose cycles of T3 to kick start the normal control. No good in low thyroid ,afaik- but interesting that the doses are 3td and stopped after a run. recent link on here about it.
This is the piece by a Dr. Dommisse (being interviewed by Mary Shomon) Nostone linked above Mary: thyroid-info.com/articles/d...
It very clearly discusses his view on the reasons why many doctors are resistant to using T3, and offers some cautions too. He seems to see the biggest problems as being simple ignorance/adherence to dogma/fear of pofessional sanctions/refusal to be led by or even to respond to patient symptoms. (which rings very true from my own experience anyway...)
I'd have to say that while I've done well as a result of increasing the proportion of T3 I take that I'm not convinced that T3 alone is necessarily on its own ideal.
Domisse reckons that T3 doesn't cross the blood brain barrier very well, but there seems to be other stuff around that maybe contradicts that and suggests that both T3 and T4 are used in the brain for different purposes - especially during development. More reading might clarify this point.
He doesn't mention the importance of correct adrenal function, and the likely need to achieve proper control of cortisol levels for metabolic health, and reduction of the risk of all three types of hypothyroidism too.
Against that his approach of not fixating on dosing replacement hormone to any particular T4/T3 ratio to an individual, but of adjusting the ratio of the two so that both free T4 (FT4) and free T3 (FT3) end up at the upper end of the reference ranges seems sensible unless it doesn't deliver results in practice - it's hard not to conclude that T4 may not there for some reason/that there are not channels that need it.
He's commendably clear that if TSH is higher than 0.1 - 1.0 or FT3 and FT4 are not at the upper ends of their respective ranges that hypothyroidism is very possible depending on the individual - and that ultra cautious replacement by many doctors leaves many in this situation. He's also clear that almost everybody needs some T3 to optimise their replacement - that very few can convert enough from T4.
One big question left unanswered to my mind in the piece is what's going on in the case of those who have found that running even lower TSH and blood levels of T3 that are well above the reference ranges is needed for them to feel well. There's fairly clearly something about their health status or their physiology that means it works for them, but it'd be worrying if there was the possibility of that factor X suddenly reversing or being eliminated to leave them significantly hyper....
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
Sorry Mary - it wasn't my intention to try to put you on the spot - it was intended more as a rhetorical question.
Sorry no link, it's from an ad site, but still a good read: Improving Thyroid Hormone Conversion
Question to those who have tried NDT alone and NDT + T3
A thyroid hormone network exists in synovial fibroblasts of rheumatoid arthritis and osteoarthritis patients
Very interesting study just released
