Potency of T3 vs T4 medications

[goolarra]

I have read that T3 is "several times" more potent than T4, when taken for hypothyroidism.  Does anyone know specific numbers? range?  For example, if I wanted to replace 25mcg of T4 with T3, how much T3 would that be?

[bizwiz12751]

Unfortunately, thyroid medicine causes great frustrations for the patient. It takes so long to level out and I've seen many people do more harm by trying to make too many dose switches and not give the medicine time to work through the body. That's a great point, many times vitamin deficiencies do act as thyroid symptoms. So, although it's frustrating, hang in there and it will work out.

[Smilerdeb]

I totally agree with you in regards to not taking T3 on its own because of its potency.
I suffer with 'drug sensitivity' so at present T3 is not an option for me.
I have had to 'wait the distance' and it has finally paid off. My TSH has gone down from 3.8 to 2.3 in 11 days without making the Free T's go too high. I have to increase my T4 in .25mcg increments too as I suffered with Atrial Fibrillation prior to Rai (Graves and Hyperthyroidism).
I am currently on .75mcg T4 and expect another increase to .88mcg within the next 2 weeks.
As they say....baby steps all the way.
My Doctor tried increasing my T4 in .50mcg increases and I went hyper so had to start from scratch all over again.
Its been 5 months post RAI and I am normal Free T's and TSH is coming down doing it 'slowly.
There was a question at one stage where it was thought I had conversion problems but  it seemed to even itself out slowly.
I feel great now, especially since I had my vitamin levels checked and found to be deficient in Zinc, Vit. D, B12.and now take these supplements.
Magnesium took away the aches in the legs and burning of the feet that a lot suffer with Graves Disease.

[bizwiz12751]

Absolutely correct! It's best to add T3 as an overall total, wait 6 weeks, take blood work to check for free T3 and free T4 and adjusting the dosage accordingly. It's been 2.5 years since my TT and I've finally been on the one dose for longer than 3 months. I can build a pyramid with the left over medicine bottles of T4 and T3 medicine from experimenting so much with the dosages. So, finally, it looks like 175 mcg of Synthroid (taken @ 5:30 am) and 5 mcg of Cytomel at 7:30 am and another 5 mcg of Cytomel at 1:30 pm is what's keeping me sane. Everybody's different and you definitely have to use your common sense when you are talking to the doctors.

[bizwiz12751]

The dosage is determined depending on a patient and the symptoms. However, the medicine potency itself, which is what goolarra was asking, usually T3 is 2 or 2.5 times stronger than T4. For example, 25 mcg Cytomel would equal approximately 50 mcg of Synthroid. As I stated, T3 is immediately absorped so the dosage may have to be split in two or even three doses depending on symptoms and/or other medications. Many people have conversion problems with T4. I, personally, would never take T3 alone, but combined with T4 it certainly made me feel human again.


  

[goolarra]

Thanks.  I agree - I've heard T4/T3 ratio of 4:1 or sometimes 3:1, the latter to clear up brain fog.  Unfortunately, my current doctor (soon to be former) really doesn't seem to have any idea what's going on.  When I was taking 50 mcg T4, she suggested adding a "little" T3.  a couple of keystrokes later and she wanted to drop my T4 to 25 mcg and add 25mcg T3, with never any mention of splitting the dose.  I protested loudly, and she begrudgingly settled on 5mcg T3 and lowered the T4 to 25mcg.  It didn't work out (surprise, surprise).  I just feel that in making changes, it's really important to only change one variable at a time - if you introduce T3, then you should probably keep the "overall" dose of T3 + T4 about the same as what you were taking before adding the T3.  Then you see what the "new" variable is actually doing.  Thus, the question.  Thanks for reminding me about splitting the dose.  I'm working on questions for a new doc, and you just reminded me of one more.
AJ

[Smilerdeb]

I may be wrong but usually the dosage of T3 is determined by how much T4 is being taken.
Usually it is 80% T4 and 20% T3 and it is unadvisable to take T3 on its own.
T4 is absorbed in the bloodstream, goes to the liver which then converts it to T3.
Taking T3 on its own doesnt do this.
It doesnt stay in your system for long so you have 'highs' and 'lows' of medication.
If you are concerned, I would ask your Doctor.