16th April 2007
Ok, I'll try my hand at answering this. The usual disclaimer here: I'm not a medical doctor, consult a doctor before any change in meds, blah blah blah ...
Ok good, glad we got that out of the way.
A healthy thyroid produces both T4 (thyroxin) and T3 (triiodothyronine). However, it only produces about 1/5 as much T3 as it does T4. The T4 by itself is not used directly - it is converted in other parts of the body (sorry don't know exactly where or how) into T3, in which form it is useful to tissues in your body.
Synthroid is a T4 only drug. There are others ... Cytomel is a T3 only drug. Again, there are other brands.
So when people discuss taking T4 they are really talking about taking their Synthroid pill, or Unithroid, or any other T4-only drug. When people talk about taking their T3, they are really talking about taking their Cytomel (or some equivalent brand). Same thing.
Some drugs, such as Armour (dessicated thryoid extract) contain both T3 and T4.
Modern medical theory says that when the thyroid fails (hypothyroidism), all that's needed is to replace the T4 (even though your thyroid produces T3 as well) since the T4 gets converted to T3 anyway. In other words, the fact that your thryoid produces T3 doesn't really matter, since tissues can draw as much T3 as they need by converting T4, so replacing T3 is not considered necessary. Several medical studies demonstrate that adding T3 does not help the patient feel any better. However, some patients strongly feel that they DO feel better with T3 added, despite what the studies say.
I can't comment on the efficacy of T3 since I have never taken it. I can say that I have many frustrating symptoms that have cropped up about a year after I was diagnosed with Hashimotos, and that I suspect that there is more to the story than modern medical science understands.
Loretta38, I hope this at least partially answered your question, sorry if I am telling you stuff that you already know.
If anyone wants to clarify or correct, please go ahead ...
Ok good, glad we got that out of the way.
A healthy thyroid produces both T4 (thyroxin) and T3 (triiodothyronine). However, it only produces about 1/5 as much T3 as it does T4. The T4 by itself is not used directly - it is converted in other parts of the body (sorry don't know exactly where or how) into T3, in which form it is useful to tissues in your body.
Synthroid is a T4 only drug. There are others ... Cytomel is a T3 only drug. Again, there are other brands.
So when people discuss taking T4 they are really talking about taking their Synthroid pill, or Unithroid, or any other T4-only drug. When people talk about taking their T3, they are really talking about taking their Cytomel (or some equivalent brand). Same thing.
Some drugs, such as Armour (dessicated thryoid extract) contain both T3 and T4.
Modern medical theory says that when the thyroid fails (hypothyroidism), all that's needed is to replace the T4 (even though your thyroid produces T3 as well) since the T4 gets converted to T3 anyway. In other words, the fact that your thryoid produces T3 doesn't really matter, since tissues can draw as much T3 as they need by converting T4, so replacing T3 is not considered necessary. Several medical studies demonstrate that adding T3 does not help the patient feel any better. However, some patients strongly feel that they DO feel better with T3 added, despite what the studies say.
I can't comment on the efficacy of T3 since I have never taken it. I can say that I have many frustrating symptoms that have cropped up about a year after I was diagnosed with Hashimotos, and that I suspect that there is more to the story than modern medical science understands.
Loretta38, I hope this at least partially answered your question, sorry if I am telling you stuff that you already know.
If anyone wants to clarify or correct, please go ahead ...