I have come across inconclusive information on this issue...
One source says the temporary spike of serum FT3 level a couple of hours after exogenous T3 administration is not dangerous.
Then again another source says the opposite...
Could you enlighten me, please?
Thank you!
Spiking should be avoided as much as possible by dose splitting. After all, in health there are no T3 spikes. What happens is that the spike changes temporarily how your body is working and this carries on for a while after the spike has gone. Though this might not matter in the short run, over a lifetime the small effects add up and when you are older could have caused problems.
I agree with Diogenes to some extent. I would split any T3 containing medication into two or three daily doses. At one time I was on high doses of L-T3, up to around 100 mcg daily. I needed this to overcome what was clearly a form of resistance to thyroid hormone. I used a heart rate monitor to monitor my heart rate overnight and rather surprisingly my heart rate was steady overnight with no peaks after taking the L-T3. Thyroid hormone receptors need to be saturated with T3 for several hours for hormone action to take place. I assume this is why we don't get a sudden response when taking T3. However, there are some 'non-genomic' effects of T3 which respond rapidly to the hormone.
Perhaps a bigger issue is that if we take TSH suppressive doses of T3 for a long time there is a risk of atrial fibrillation and stroke and possibly bone loss. Although we may have a peripheral resistance to thyroid hormone this may be specific to certain receptors and not the whole body. Consequently a dose that resolves our symptoms in most organs may be too much for other organs such as the heart.
My approach is to split doses and try to make sure I'm on the minimum effective dose. Bear in mind that a perfectly safe dose may be too little to give a reasonable standard of life. This applies to many disorders, not just hypothyroidism. Sometimes we can't reach perfection and have to compromise between risk and having a life.
Endocrinologists confuse 'pharmacokinetics' how the body absorbs and eliminates the drug with 'pharmacodynamics' how the drug affects the body. Thus they will state that the peaks (as measured by an assay) are dreadful, where in practice the harmful effects are much less because it takes some time for T3 to act on our cells. A large number of prescription drugs have short half lives and so produce much sharper peaks than T3. A bit of common sense is needed.
And yet... The wonderful Dr Lowe took a huge dose of T3 every night for years...
Yes but he was a T3 resistant and could take it without as many problems.
Perhaps for 'ordinary' folk, dosage of, say, 150mgs of NDT might not produce unwanted effects? On the basis that one is only looking at around 9mcgs of T3... Dr Lowe suggested taking one dose in the morning, however, some folk do seem to do better on a split dose regime. I'm thinking of trying it myself. Although, I'm not sure if 4.5mcgs of T3 per dose will hit the mark. Mind you, some T4 will convert. It's a minefield, this 
Dr Lowe required very high doses indicating resistance. My belief is that these patients need T3 rather than T4 in order to bypass deiodinase mechanisms that try to maintain steady cellular T3 levels. Unfortunately, different organs have different receptors and deiodinase activity. The brain is particularly effective at maintaining normal T3 levels. Thus if you go solely by how you feel you may make other organs thyrotoxic. Hence, my suggestion that sometimes there has to be a compromise.
Dr Lowe had severe resistance, as indicated by his need to take 150 mcg L-T3. He took it in a single dose. I prefer two doses, not least because I have found the night-time dose more cruical to eliminating cognitive impairment. Dr Lowe was well able to monitor his response and would have needed to be fully medicated to carry out his invaluable research. If patients are on high dose T3 medication (which supresses their TSH) it would be a good idea to consider asking their GP to put them on low dose beta-blocker to protect their heart.
The only safe option is to discover the cause of this form of resistance and eliminate it.
This is a helpful explanation. I stopped taking T3 (only 10mcg plus 110 T4) as I developed atrial fibrillation. I have tried re-introducing T3 with a lower dose of T4 but I seem to have developed a sensitivity to T3 and feel it is causing palpitations. I am trying 5mcg a day in two doses but still feel an adverse effect. Am going to try the micro dose route.
I am doing this very small micro dose in the morning it just tops up my t3 as my t4 is converting and absorbing but not brilliantly,it keeps me going in the day but has lost power by the early evening and I sleep well. I am hoping in the winter when I need a seasonal adjustment then I will increase the t3.(that's the plan any way) trial and error.
I was on T3 only for nearly fifteen yrs and became accustomed to knowing how it made me feel if a little low or a little high. I always split my dose throughout the day as unable to take it all together without issues. I used to take the doses around the same time but could always tell when I needed it again and waited until then. The few times I took it a little early and could tell that it was spiking, was always within 15 minutes of taking it and if this happened, I would down a pint of milk to help stop absorption of what remained in my stomach- always seemed to calm it down quickly. This was generally not normally a problem though as long as I waited until I needed it - normally within a two hour time frame.
I did start to have massive problems with spiking and nausea once my body stopped producing T4 of its own for some reason even though my blood tests did not correspond to hyper - looked more hypo? This also seemed to massively make more apparent the different requirements in different parts of my body. I had to run my thyroid low with tsh of around 7-10 for six months until I figured it out as was preferable to the hyper. Have now added T4 back in and these problems appear to have dissipated.
Although I appear to now have a separate issue with the T4 - my body just does not like it but better than the alternative - I think so far lol!
Ft3 295% 3 hours after dose, taking 95 t4 and 30 t3 in one go (Armour and Thybon T3)
Is T3 from conversion within the cell shown in fT3 blood result?
After a reduction in FT3 meds, how long before FT3 reduces and T4 increases?
NDT blood test- how long after taking the dose?Is FT4/FT3 ratio sometimes important? Does taking T3 enhance T4/T3 conversion? And in seek of advice? 
