Direct and rapid effects of 3,5-diiodo-L-thyronine (T2)

Slowly, so very slowly, evidence is accumulating that the impact of thyroid hormone is far more complicated than turning the wick up - or down - a bit.

(Although many peope have claimed the T2 content of desiccated thyroid is responsible for some of its impact, I tend to the view that the amount present is likely so small as to have virtually no impact. I could be wrong. Even if I am, no-one controls the amount of T2 that is present so it really could vary quite a bit.)

Mol Cell Endocrinol. 2017 Feb 9. pii: S0303-7207(17)30092-8. doi: 10.1016/j.mce.2017.02.012. [Epub ahead of print]

Direct and rapid effects of 3,5-diiodo-L-thyronine (T2).

Moreno M1, Giacco A1, di Munno C1, Goglia F2.

Author information

1Department of Science and Technologies, University of Sannio, Benevento, Italy.

2Department of Science and Technologies, University of Sannio, Benevento, Italy. Electronic address:


A growing number of researchers are focusing their attention on the possibility that thyroid hormone metabolites, particularly 3,5-diiodothyronine (T2), may actively regulate energy metabolism at the cellular, rather than the nuclear, level. Due to their biochemical features, mitochondria have been the focus of research on the thermogenic effects of thyroid hormones. Indeed, mitochondrial activities have been shown to be regulated both directly and indirectly by T2-specific pathways. Herein, we describe the effects of T2 on energy metabolism.

Copyright © 2017. Published by Elsevier B.V.


3,5-Diiodothyronine; Energy metabolism; Metabolic rate; Mitochondria; Short-term effects; Thyroid hormone action

PMID: 28192176

DOI: 10.1016/j.mce.2017.02.012

12 Replies

  • That's we have tests for T2? Is it possibly a missing link in diagnosing 'normal', 'in-range' but definitely symptomatic folk?

  • On the basis that most T3 conversion to T2 occurs within cells, I think any measuring of T2 in readily available fluids (blood, spit, urine) would be useless.

    We need also to remember that rT3 also converts to T2. I really do question everything that ever seems obvious about rT3.

    Does that mean that the total T2 available to our bodies is, more or less, based on the total of T3 plus rT3 that passes through?

  • There is an academic one in Germany but I don't think yet that they have used it as a diagnostic.

  • Thank you. More evidence that thyroid hormones are more than T4 alone.

  • Hmmmm.... Some time ago, i had a tft test, which i remember showed below range Rt3. I just thought that was probably good, but could it be that i have low t2 as a result?

    Have heard before that t2 is the bit that sorts out if we are fat or not. I am still having an awful time losing weight... Have just thrown away 4 years worth of lists which listed everything i ate....

    Thanks for posting Helvella.

    Xx g

  • I'd love to give you an answer other than the only one I can - I don't know!

    Could speculate, with varying degrees of understanding and wishful thinking, but that is all it would be. Nothing wrong in doing so, but so very important to separate speculation from reporting.

  • Hypothesise, then experiment is a reasonable way to work things out. Shame the way our medics work is the same as the ancient Greeks. The Greeks put all the learned people together and they would talk and form opinions, which were regarded as fact, but they never experimented.

    Xx g

  • I think I'd put some of those ancients ahead of most endocrinologists. :-)

    They did do some practical things, even if not generally in the nature of scientific experimentation. Like the quite astonishing antikythera.

  • Quite an astounding machine - thanks for the link.

    Your first comment made me laugh out loud! I presume their ban on dissection held back medical knowledge.

    I understood the Greeks believed thought resided in the heart and the brain just cooled the blood down, but it seems one group of ancient thinkers were correct about the true function of the brain as the centre of thought.

  • Apologies...what's a 'tft test' please?

  • Holy f***, Rodders. Mitochondrial dysfunction is cited as one of the causative factors in that great hypochondriacal mental-health problem with screeds of empirical data to support a systemic cause, Myalgic Enephalomyelitis. How very interesting.

  • Common sense tells me if we have it it must be necessary but if it is a product degeneration then may be not but interesting that it is being looked into. Something that we should keep an open mind on and report any further info I think.

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