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.
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