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Evolutionary roots of iodine and thyroid hormones in cell–cell signaling

Evolutionary roots of iodine and thyroid hormones in cell–cell signaling

This is NOT going to be everyone's cup of tea! But if you feel it could be interesting, have a dip and see if it is to your taste. You are not going to get anything useful from it (e.g. do something to make you better) - however fascinating it is. And it is not even newly published!

Also by the same author:

Rhythms of Life: Thyroid Hormone and the Origin of Species

Integr. Comp. Biol. (2009) 49 (2): 155-166. doi: 10.1093/icb/icp053 First published online: June 23, 2009

Evolutionary roots of iodine and thyroid hormones in cell–cell signaling

Susan J. Crockford1

+ Author Affiliations

Department of Anthropology, PO Box 3050 STN CSC, University of Victoria, British Columbia, Canada V8W 3P5



In vertebrates, thyroid hormones (THs, thyroxine, and triiodothyronine) are critical cell signaling molecules. THs regulate and coordinate physiology within and between cells, tissues, and whole organisms, in addition to controlling embryonic growth and development, via dose-dependent regulatory effects on essential genes. While invertebrates and plants do not have thyroid glands, many utilize THs for development, while others store iodine as TH derivatives or TH precursor molecules (iodotyrosines)—or produce similar hormones that act in analogous ways. Such common developmental roles for iodotyrosines across kingdoms suggest that a common endocrine signaling mechanism may account for coordinated evolutionary change in all multi-cellular organisms. Here, I expand my earlier hypothesis for the role of THs in vertebrate evolution by proposing a critical evolutionary role for iodine, the essential ingredient in all iodotyrosines and THs. Iodine is known to be crucial for life in many unicellular organisms (including evolutionarily ancient cyanobacteria), in part, because it acts as a powerful antioxidant. I propose that during the last 3–4 billion years, the ease with which various iodine species become volatile, react with simple organic compounds, and catalyze biochemical reactions explains why iodine became an essential constituent of life and the Earth's atmosphere—and a potential marker for the origins of life. From an initial role as membrane antioxidant and biochemical catalyst, spontaneous coupling of iodine with tyrosine appears to have created a versatile, highly reactive and mobile molecule, which over time became integrated into the machinery of energy production, gene function, and DNA replication in mitochondria. Iodotyrosines later coupled together to form THs, the ubiquitous cell-signaling molecules used by all vertebrates. Thus, due to their evolutionary history, THs, and their derivative and precursors molecules not only became essential for communicating within and between cells, tissues and organs, and for coordinating development and whole-body physiology in vertebrates, but they can also be shared between organisms from different kingdoms.

<much, much more by following link>


9 Replies

also includes Hibernation, my favourite subject.

Origin of species rings a bell - he lived in Shrewsbury you know, we have a large concrete bone structure to remind us. I have extra neck ribs to remind me I'm actually a lizard and not just a cheeky monkey J :)


Yes - the Darwin Centre.



Close, it's called the 'Quantum leap' (into the river) - is there a T-shirt? I have a Dejavue moment here, sorry, interesting info on Iodine - is it on Mars I wonder? J :D


A very good question. Yes - and some interest in why the amounts are more similar to Earth than would be expected if there had never been life there.


Very interesting Rod, thanks.


hey ROD GOOD FIND, i will prob but that. very interesting. pettals


that was meant t o be BUY IT ----NOT BUT IT!!


Ros, if you haven't already read Dr. Derry's book, "Breast Cancer and Iodine" you might find it a good read. He talks about iodine and its evolution and roll in the cell amoung other things. Some interesting reviews on the book "Rythms of Life". PR


I have not read the book but have read some of his words.

His is a good demolishing of the "iodine patch test" which comes around like a bad penny.

I actually had a minor email interaction with Susan Crocker. Very interesting lady. And I feel she is looking in areas which might eventually prove fruitful.


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