Thyroid hormones in the regulation of brown adipose tissue thermogenesis

[helvella]

This paper is the fourth most-cited in 2023 from the Endocrine Connections journal.

Basic thyroid research is interesting. It is read. Scientists and some medical professionals do want more understanding. As do patients.

It gets pretty complicated but the point is, thyroid hormone controls temperature by affecting the burning of fuel in Brown Fat (B AT). And the impact of thyroid hormone is subtle with small changes in levels sometimes having different effects to larger changes.

(I think I posted some time ago but things move so fast that doesn't seem very important!)

Thyroid hormones in the regulation of brown adipose tissue thermogenesis

in Endocrine Connections

Authors: Sarah Christine Sentis, Rebecca Oelkrug, and Jens Mittag

Abstract

A normal thyroid status is crucial for body temperature homeostasis, as thyroid hormone regulates both heat loss and conservation as well as heat production in the thermogenic tissues. Brown adipose tissue (BAT) is the major site of non-shivering thermogenesis and an important target of thyroid hormone action. Thyroid hormone not only regulates the tissue’s sensitivity to sympathetic stimulation by norepinephrine but also the expression of uncoupling protein 1, the key driver of BAT thermogenesis. Vice versa, sympathetic stimulation of BAT triggers the expression of deiodinase type II, an enzyme that enhances local thyroid hormone availability and signaling. This review summarizes the current knowledge on how thyroid hormone controls BAT thermogenesis, aiming to dissect the direct actions of the hormone in BAT and its indirect actions via the CNS, browning of white adipose tissue or heat loss over body surfaces. Of particular relevance is the apparent dose dependency of the observed effects, as we find that minor or moderate changes in thyroid hormone levels often have different effects as compared to high pharmacological doses. Moreover, we conclude that the more recent findings require a reevaluation of older studies, as key aspects such as heat loss or central BAT activation may not have received the necessary attention during the interpretation of these early findings. Finally, we provide a list of what we believe are the most relevant questions in the field that to date are still enigmatic and require further studies.

Keywords: thermogenesis; BAT; thyroid hormone receptor; uncoupling protein 1; heat loss; adrenergic sensitivity

ec.bioscientifica.com/view/...

[Charlie-Farley]

I like it, yes I’m not following the detail but get the main message- I think😂. Huberman was talking about brown adipose tissue on a podcast. He is so interesting but the two hour information sense podcasts leave me needing to go and have a lie down. 🤯

Especially like the reviewing previous studies angle. If only they realised the extent of reviewing that needs to happen.

[helvella Administrator Thyroid UK in reply to Charlie-Farley]

It isn't many years ago they used to more or less assert that adult humans had no, or virtually no, Brown Adipose Tissue.

Add to that the discovery of Ghrelin and Leptin. The reclassification (by some) of skin as an endocrine organ. The concept of vitamin D as a hormone (or at least, hormone-like substance).

The basic science and some theory has come on apace. But getting it from there into medical practice is another matter altogether.

[Charlie-Farley in reply to helvella]

Oh yes……🙄👍

[Lottyplum in reply to helvella]

Precisely! How to get it to the GPs who are doling out their wisdom+prescriptions is quite another thing!

[nightingale-56 in reply to helvella]

My Son's Endo at UCL was doing research into Leptin and Ghrelin and used my Son (with permission) in part of his research in about 95/96. My Son did not mind as he got a Mars Bar out of it for just using a running machine for a short while. We did not have any further imformation about this though.

[wellness1 in reply to Charlie-Farley]

That's how I feel after a Huberman podcast.

As helvella points out, getting it all into clinical practice takes time...

[Charlie-Farley in reply to wellness1]

Ooh, I’m glad I’m not the only one!🤣👍

[ColderThanIce2]

Thanks. I think this is behind why I'm so cold all year round:

"we find that minor or moderate changes in thyroid hormone levels often have different effects"

I still reckon my T3/4 levels dropped to a level lower than I used to have, but are still within "the range".

[Charlie-Farley in reply to ColderThanIce2]

Hi Colder

Where you sit in the range is relevant. Perhaps you need to review where you are at? If you are on mono therapy (T4) and read the NICE guidelines there is a guide (and it is only a guide not an edict) of 1. 6 µg per kilogram of levothyroxine. So I’m 15 stone. (yes, I need to work on that!) And I’m on 150 µg of levothyroxine as a therapeutic dose.. My TSH is below range and will probably freak out my new GP but my thyroid hormones both sit within range and actually have dropped a little but I’m feeling great so that’s the main thing as symptoms should be the primary determinant for treatment. Not how good the blood work looks. There are pinned posts that you may find useful. 😉👍