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Liothyronine conversion to NP Thyroid
My doctor would like to change me back over to NP Thyroid, which I am okay with. I am currently on 15 mcg of liothyronine and 125 mcg of Levothyroxine. The order she sent to the pharmacy is 60mcg NP in the am and 15mcg in pm. I understand from the conversion chart the 125 mcg converts to the 60/15 mcg but that doesn't take into account the additional 15mcg of liothyronine that I was on.
The comment made during my appointment was that we need to get my free t3 up but won't the med change lessen my dose of T3?
I could not find a resource for a conversion of liothyronine to NP Thyroid. Is there a source for this?
Prior history: prior to switching to the T3/T4 meds I was on 90 mcg NP Thyroid + 25mg synthroid for 4 days a week and 135 mcg NP (1.5 pills) + 25 my of synthroid 3 days a week. Changed 6 most ago to get T4 up.
Thank you!
The comment made during my appointment was that we need to get my free t3 up but won't the med change lessen my dose of T3?
I could not find a resource for a conversion of liothyronine to NP Thyroid. Is there a source for this?
Prior history: prior to switching to the T3/T4 meds I was on 90 mcg NP Thyroid + 25mg synthroid for 4 days a week and 135 mcg NP (1.5 pills) + 25 my of synthroid 3 days a week. Changed 6 most ago to get T4 up.
Thank you!
The amount prescribed by your NP is not even close to an equivalent amount of thyroid med. One grain (60 mg) of NP Thyroid has 38 mcg of T4 and 9 mcg of T3. To get to close to the 125 mcg of T4 and 15 mcg of T3 you are currently taking would require 150 mg of NP thyroid. This is how to figure it out.
The usual assumption is that for its effect on TSH, 1 mcg of T3 is equal to 4 mcg of T4. Some recent studies have shown that the ratio should be 3 : 1. If you assume the 3:1 ratio and apply it to your prior split dose, that would average about 139 equivalent mcg of T4. Your current dose would be 125 + 3 times 15 = 170 equivalent mcg of T4. To be close to that amount would require 2 1/2 grains of NP Thyroid, which is about 150 mg and would give you 162 mcg of equivalent T4. The proposed new dose would be only 82 equivalent mcg of T4 (47.5 mcg of T4 + 11.5 mcg of T3 times 3 = 82), which is far too little.
Probably the easiest way to disagree with the NP on your new dose is to approach it from the standpoint of how many mcg of T4 and T3 are in your current dose that works well for you. Of course it is 125 plus 15. What is the dose of NP Thyroid that gets you closest to those amounts? One grain of NP, or 60 mg provides 38 mcg of T4 and 9 mcg of T3. Two grains , or 120 mg, would get you to 76 of T4 and 18 of T3, which is considerable less than current T4 and slightly more than current T3. So you really need 2 1/4 to 2 1/2 grains of NP Thyroid ( 135 - 1 50 mg ) to stay where you are.
I suggest that you not let the NP try to use the conversion tables to continue with the 90 + 15 dose. The conversion tables are very misleading. I can explain that if you want, but I would just stick with the above argument.
When you do make the switch, note that your FT3 woill build up faster than your Free T4 drops, so it would be advisable to make the change in two steps several weeks apart. I know splitting dosages is a pain, but do the best you can for the transition.
The usual assumption is that for its effect on TSH, 1 mcg of T3 is equal to 4 mcg of T4. Some recent studies have shown that the ratio should be 3 : 1. If you assume the 3:1 ratio and apply it to your prior split dose, that would average about 139 equivalent mcg of T4. Your current dose would be 125 + 3 times 15 = 170 equivalent mcg of T4. To be close to that amount would require 2 1/2 grains of NP Thyroid, which is about 150 mg and would give you 162 mcg of equivalent T4. The proposed new dose would be only 82 equivalent mcg of T4 (47.5 mcg of T4 + 11.5 mcg of T3 times 3 = 82), which is far too little.
Probably the easiest way to disagree with the NP on your new dose is to approach it from the standpoint of how many mcg of T4 and T3 are in your current dose that works well for you. Of course it is 125 plus 15. What is the dose of NP Thyroid that gets you closest to those amounts? One grain of NP, or 60 mg provides 38 mcg of T4 and 9 mcg of T3. Two grains , or 120 mg, would get you to 76 of T4 and 18 of T3, which is considerable less than current T4 and slightly more than current T3. So you really need 2 1/4 to 2 1/2 grains of NP Thyroid ( 135 - 1 50 mg ) to stay where you are.
I suggest that you not let the NP try to use the conversion tables to continue with the 90 + 15 dose. The conversion tables are very misleading. I can explain that if you want, but I would just stick with the above argument.
When you do make the switch, note that your FT3 woill build up faster than your Free T4 drops, so it would be advisable to make the change in two steps several weeks apart. I know splitting dosages is a pain, but do the best you can for the transition.
2 Comments
Thank you so much! My appointment to discuss the med change and my concerns is tomorrow morning, and you have given me great information to help present my case and my desired treatment plan.
Please let us know how it goes.
Before answering your question about conversion, please tell us about any symptoms you have currently and also give us your test results for Free T4 and Free T3, along with reference ranges shown on the lab report.
2 Comments
I am feeling the best I have felt in a very long time. The reason for the switch is myborior doctor left the practice and the new one prefers NP Thyroid.
Free T3 = 3.2 (range 2.0 - 4.4)
Free T4 = 1.17 ( range .82 - 1.77)
TSH = .312 (range .450 - 4.5)
Free T3 = 3.2 (range 2.0 - 4.4)
Free T4 = 1.17 ( range .82 - 1.77)
TSH = .312 (range .450 - 4.5)
Edit to read: “my prior doctor left the practice and the new one prefers…”
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