It's Official - Low Testosterone Suppresses T4 To T3 Conversion / Lowers Metabolism

youngandold

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Joined
Nov 17, 2015
Messages
87
Study shows low testosterone suppresses D1 deiodinase, the enzyme that converts T4 to T3, in the liver
Regulation of rat liver type 1 iodothyronine
deiodinase mRNA levels by testosterone
Regulation of rat liver type 1 iodothyronine deiodinase mRNA levels by testosterone

Besides the testosterone-thyroid connection, this study shows that high TSH increases T4 to T3 conversion
Orchidectomy of middle-aged rats decreases liver deiodinase 1
and pituitary deiodinase 2 activity
http://m.joe.endocrinology-journals.org/content/215/2/247.full

Testosterone and estradiol treatments differently affect
pituitary-thyroid axis and liver deiodinase 1 activity in
orchidectomized middle-aged rats
Testosterone and estradiol treatments differently affect pituitary-thyroid axis and liver deiodinase 1 activity in orchidectomized middle-aged rats. - PubMed - NCBI

Testosterone increases T3 to T4 ratio in transformers
The effects of sex-steroid administration on the pituitary–
thyroid axis in transsexuals
Eur J Endocrinol | Mobile
 

Giraffe

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Jun 20, 2015
Messages
3,730
Besides the testosterone-thyroid connection, this study shows that high TSH increases T4 to T3 conversion

"In conclusion, our results demonstrate that orchidectomy of rats at middle age induced changes in thyroid structure with no effect on serum T4 and TSH. However, decreased activities of DIO1 in the liver and DIO2 in the pituitary indicate tissue compensation or adaptation through changes in local production of T3."
How does this show that high TSH increases T4 to T3 conversion? :confused2
 

narouz

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Joined
Jul 22, 2012
Messages
4,429
I admit I haven't looked carefully at the study,
but just based on many things I've looked at over the years
I would be much more inclined to think the causality would be the other way around.
Personally, I've had prolonged underachieving thyroid function
despite having okay testosterone levels.
 

Explorer

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Joined
Oct 7, 2020
Messages
499
Isn't Testosterone synthesis done with use of T3+Pregnanolone too so when you have less T3 you have less Testosterone and then less conversion of T4>T3 and then even less Testosterone creating a feedback loop for hypogonadism?
 

Nebula

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Joined
May 30, 2018
Messages
677
Isn't Testosterone synthesis done with use of T3+Pregnanolone too so when you have less T3 you have less Testosterone and then less conversion of T4>T3 and then even less Testosterone creating a feedback loop for hypogonadism?
So would that suggest T4 supplementation might not be effective if testosterone is low. Maybe micro doses of T3 would be more effective in that case. I’m currently microdosing tyromix. It increases temperature for a few hours, but then I feel a little wired. Maybe I’m not converting the T4 due to low T and other factors. I might switch to microdosing T3 only.
 

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