Thyroid hormones in the regulation of brown adipose tissue thermogenesis

[helvella]

We keep seeing that thyroid hormone is required by every cell of the body. We can see some specific effects - hair loss, myxoedema (mucinous deposits), etc. - but all too often we have no detail whatsoever. Just a general observation that we are more healthy with sufficient thyroid hormone than insufficient.

This paper looks very much at the impact of thyroid hormone on brown fat cells. It is in them that we can produce heat to keep us warm - without shivering or other muscle activation. If that is not working well, our body temperature will likely drop, and we will have limited ability to warm ourselves up once we get cold.

Thyroid hormones in the regulation of brown adipose tissue thermogenesis

DOI: doi.org/10.1530/EC-20-0562

Volume/Issue: Volume 10: Issue 2

Page Range: R106–R115

Article Type: Review Article

Online Publication Date: Feb 2021

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/...

[tattybogle]

What's this ? .. actual SCIENCE looking at minor/moderate changes in thyroid hormone levels.... hurrah !

(but wait ..... surely they've forgotten to suggest that the adipose tissue might be somatising, and could benefit from counselling ? )

[helvella Administrator Thyroid UK in reply to tattybogle]

And/or anti-depressants?

[TSH110 in reply to tattybogle]

And if you’re old, no thyroid hormone therapy at all

[AmandaK]

The authors are women, so they are bound to be ignored

😉

[helvella Administrator Thyroid UK in reply to AmandaK]

Or sued:

World expert in scientific misconduct faces legal action for challenging integrity of hydroxychloroquine study

Australian and international scientists publish open letter defending Dr Elisabeth Bik and calling for science whistleblowers to be protected

theguardian.com/science/202...

[AmandaK in reply to helvella]

We seem to be living in a world where there is no integrity any more. Nor the desire for it. Seems to be endemic in so many areas of life and those seeking after truth are systematically gagged. Or maybe it was forever thus and I'm being idealistic?

[Elston]

Wow I found this very interesting to read, but was does adrenergic sensitivity mean? ..what coudhappen? Karen.

[helvella Administrator Thyroid UK in reply to Elston]

Wiki defines "adrenergic":

Adrenergic means "working on adrenaline (epinephrine) or noradrenaline (norepinephrine)" (or on their receptors). When not further qualified, it is usually used in the sense of enhancing or mimicking the effects of epinephrine and norepinephrine in the body.

So adrenergic sensitivity means how sensitive a cell or receptor is to the effects of adrenalin or noradrenalin. In context, how much effect noradrenalin has on brown adipose tissue. Insufficient thyroid hormone results in lowered sensitivity.

[Elston in reply to helvella]

Its still not really sinking in my brain but thankyou.I'm interested because I have to eat high protien diet to sustain my energy levels.

I have also got adrenal insufficiency...

Am I trying to connect your answer to me ? Its the Bat thats interested me.

Thankyou.

[helvella Administrator Thyroid UK in reply to Elston]

Everything to do with brown adipose tissue (BAT) in humans is in the melting pot.

Until a few years ago, "they" appeared to insist that adults do not have any BAT. Then it was realised that we don't have big, obvious lumps of BAT, but we do have BAT cells. Hence, much of what had been regarded as animal and human infant-only, suddenly started to become relevant.

Adrenalin and noradrenalin appear to be important factors for temperature control. But if you haven't got enough thyroid hormone, you need even more adrenalin/noradrenalin to have the same effect.

[Elston in reply to helvella]

H ok..this may explain why I feel cold constantly and takes me ages to warm up, but then once I'm warm I get too hot ? I carnt go outdoors in hot sun anymore because I overheat ..Winter is fine because I can put layers of clothes on..

Its like my body carnt control my body tempreture,?

Thankyou.

[helvella Administrator Thyroid UK in reply to Elston]

Temperature control issues are all too prevalent in thyroid disorders.

Because thyroid hormone is fundamental to the rate of metabolism - and that is what enables us (and all warm-blooded creatures) to manage our body temperature. And it also affects blood flows and sweat - which also help manage body temperature.

[Elston in reply to helvella]

Ok thankyou...

[thyr01d]

Thanks Helvella, that's really interesting, it is great the way you source and share such articles.