Thyroid Hormone Distributor Proteins During Development in Vertebrates

[helvella]

The opening sentence of this paper should, perhaps, be considered as a serious question about the possible impacts of oral thyroid hormone supplementation. If thyroid hormone affects (some) bacteria, we would expect there possibly to be an impact on gut bacteria.

And what is one of the most common issues reported by those with thyroid disorders? Could the gut issues be at least partially due to have thyroid hormone present in quantities that would never be encountered in healthy humans?

The rest of the paper (at least, the abstract - I have not yet read the full paper) is simply of general interest.

Published online 2019 Aug 8. doi: 10.3389/fendo.2019.00506

PMCID: PMC6694296

Thyroid Hormone Distributor Proteins During Development in Vertebrates

Sarah A. Rabah, Indra L. Gowan, Maurice Pagnin, Narin Osman, and Samantha J. Richardson*

Abstract

Thyroid hormones (THs) are ancient hormones that not only influence the growth, development and metabolism of vertebrates but also affect the metabolism of (at least some) bacteria. Synthesized in the thyroid gland (or follicular cells in fish not having a discrete thyroid gland), THs can act on target cells by genomic or non-genomic mechanisms. Either way, THs need to get from their site of synthesis to their target cells throughout the body. Despite being amphipathic in structure, THs are lipophilic and hence do not freely diffuse in the aqueous environments of blood or cerebrospinal fluid (in contrast to hydrophilic hormones). TH Distributor Proteins (THDPs) have evolved to enable the efficient distribution of THs in the blood and cerebrospinal fluid. In humans, the THDPs are albumin, transthyretin (TTR), and thyroxine-binding globulin (TBG). These three proteins have distinct patterns of regulation in both ontogeny and phylogeny. During development, an additional THDP with higher affinity than those in the adult, is present during the stage of peak TH concentrations in blood. Although TTR is the only THDP synthesized in the central nervous system (CNS), all THDPs from blood are present in the CSF (for each species). However, the ratio of albumin to TTR differs in the CSF compared to the blood. Humans lacking albumin or TBG have been reported and can be asymptomatic, however a human lacking TTR has not been documented. Conversely, there are many diseases either caused by TTR or that have altered levels of TTR in the blood or CSF associated with them. The first world-wide RNAi therapy has just been approved for TTR amyloidosis.

Keywords: albumin, development, evolution, phylogeny, thyroid hormones, thyroxine-binding globulin, transthyretin, vertebrates

Full paper freely available here:

ncbi.nlm.nih.gov/pmc/articl...

[JGBH]

Good point! Thanks.

[Mamapea1]

Interesting...thank you for posting👍.

[JAmanda]

Hi, I'm afraid I don't really understand what this is saying. I was looking for info on albumin as mine is always under range and it brings my magnesium under range too (there's a relationship there). Any idea what low albumin means or what I can do about it much appreciated.

Thx

[helvella Administrator Thyroid UK in reply to JAmanda]

Low albumin is sometimes a hereditary issue.

This is a short paper summarising what can cause low albumin:

ncbi.nlm.nih.gov/books/NBK5...

I quickly read through and thought it reasonably clear. Anything you don't understand, either ignore for now (some of the more complex bits are very much in the fine detail which isn't very important) or, if you need or wish, ask back.

This post is just suggesting that thyroid hormone itself might affect the bacteria in our gut. So when we swallow a levothyroxine tablet, what doesn't get absorbed could be causing some of the gut problems people report.

[JAmanda in reply to helvella]

Thanks for the info. I guess there’s not much I can do about it but I’ll see if my doc has anything to say about it.

[helvella Administrator Thyroid UK in reply to JAmanda]

Well the document does imply three possible deficiency causes:

Insufficient protein in diet

Low iron

Low zinc

If you are eating a diet which is relatively low in protein, maybe an adjustment?

And, if you can, get tested for iron and zinc deficiency. Don't go mad supplementing - too much of either is as bad as too little.

[JAmanda in reply to helvella]

No my iron and zinc are really good and I eat a pretty good diet. Lots of chicken fish eggs etc. I’ve had a dreadful stomach for years - everything gives me flatulence! - I’d hoped thyroid meds would help but possibly they can make it worse. I read about low histamine diets and take Dao and betaine Hcl enzymes - nothing helps.

My other real issue is dry eyes - I wonder if this could be related to the albumin aspect?

It’s all really complex. I’ve just been trying to get my t3 high in range (now at 72%). My t4 is only at 20% so might try to raise that.

Oh I dunno what else to do really. I’m taking a little d3 k2 and mg just to keep levels ok. Gluten free next maybe!