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T4 to T3 conversion

I had an RAI ablation after being diagnosed with Grave's disease 10 years ago and have been on levothyroxine since.  Does synthetic T4 convert to T3?  I thought that T4 to T3 conversions occurred in the thyroid gland...so without one, where does this conversion take place?

Desperately need advice as I've been miserable when my TSH is in the "normal range" and have resorted to self-treatment.
8 Responses
Avatar universal
Although both T3 and T4 are produced in a healthy thyroid, far more T4 is produced than T3.  T4 is converted to T3 primarily in the liver, but the kidneys are also involved to a lesser extent as are other organs.  Yes, synthetic T4 does convert to T3, unless you are a "slow converter".  

Please post your free T3, free T4 (and their reference ranges) and TSH.  It sounds like you are either undermedicated or might require a bit of T3 meds if your FT3 and FT4 look out of balance.  It's difficult to comment further without seeing those.
393685 tn?1425816122
I have about the same background as you with this disease. Grave's - then RAI

Goolaara is right on the mechanics of conversion.

I found it wasn't the right conversion for me as many do .

Until I found out my correct ratios of FT3 and FT4 I needed - I was lost - and sick too.

Get the labs.
649848 tn?1534637300
It's usually not a good idea to self-medicate........what are you self medicating with? What are your most recent labs and were they done before or after you began self treating.

Please post your labs if you have them, along with dosage info.

I'm on both a T4 (levo) and T3 med because I wasn't converting enough T4 to T3.  Currently, doing well.
10419551 tn?1410006149
Anyone ever explore if the could enhance T3 conversion? perhaps through diet and/or gut healing?
Why the attitude that once on HRT on it for life?
Avatar universal
Correcting a selenium deficiency can enhance conversion since the enzyme that catalyzes the conversion of T4 to T3 is selenium based.  Some conversion happens in the liver and kidneys, but a lot of it also happens right at the cell that needs it.  

By HRT do you mean thyroid hormone replacement?  The original poster had a thyroid ablation, so she has no choice but to be on replacement for life.  By far, most thyroid disease is autoimmune, Graves' or Hashi's.  Neither of those is a curable disease.  In the case of Hashi's, it's also progressive, i.e. antibodies keep destroying the thyroid until it's "dead".  
649848 tn?1534637300
What she said.  As is the case with many of us, myself included, Hashi has done so much damage that our thyroid no longer produces any hormones at all and we are dependent on the hormones we get through our daily med.  

Studies have shown that supplementing with selenium can help with the conversion of T4 to T3, but for some of us (again including myself), even that's not enough; we still have add a source of added T3.
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649848 tn?1534637300
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1756321 tn?1547098925
Queensland, Australia
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