Log in
Thyroid UK
93,557 members107,603 posts

Light Helps Regulate Salmon Smolt Transformation

There are many,many interesting avenues of thyroid research.

I found the relationship to salt fascinating.

Light Helps Regulate Salmon Smolt Transformation

11 May 2015

NORWAY - For decades, scientists have wondered what regulates changes in salmon when they transform from being freshwater to saltwater fish, and now researchers at Norway's Uni Research Ltd may be moving towards an answer.

A new study shows that light signals from increases in day length in the spring affect developmental processes in the fish's brain during smoltification.

In the recently published study, Lars Ebbesson and colleagues found that light increased the production of a special enzyme, type 2 deiodinase, activating the thyroid hormone in the smolt brain.

This enzyme stimulates the fish to prepare itself before it moves from freshwater out into salt water.

Mr Ebbesson said that previously: "We have presumed that changes in thyroid hormones have been important for normal smolt development, but we have not known how the hormone is activated and it specific roles."

They also found an important change in a similar enzyme in the gills. The gills are important for regulating the salt balance in the fish.

In the study, they found that this gill enzyme that activates the thyroid hormone in the gills only increases when the fish reaches saltwater.

The present study may explain why previous work on thyroid hormones and gill development in smolts, which have focussed on the freshwater parr-smolt transformation, have found thyroid hormones to have a minimal role.

- See more at: thefishsite.com/fishnews/25...

4 Replies

Helvella, Preparing the thyroid to accept iodine via salt water?


Though the actual iodine content of seawater is very low. The throughput of water required by, say, kelp in order to accumulate large amounts of iodine is prodigious.


The role of daylight on type 2 deiodinase is interesting, as many people anecdotally report needing less thyroxine in summer.


In human beings sunlight on the skin creates vitamin D . There have been several studies recently of the positive effect of vitamin D on the thyroid and, probably more importantly, of vitamin D's effect on autoimmune conditions. Some are mentioned here : holtorfmed.com/vitamin-d-au...


You may also like...