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Tyrosine and Thyroid Health

Published April 20 2015

Tyrosine is a non-essential amino acid, and it is involved in the synthesis of thyroid hormone.  As a result, many thyroid support formulas aimed at people with hypothyroid conditions include tyrosine.  But should people with thyroid conditions, specifically those with hypothyroidism and Hashimoto’s Thyroiditis, increase their intake of tyrosine?

Before answering this question I’d like to discuss what happens during thyroid hormone synthesis.  In the thyroid epithelial cell, iodide is converted to iodine with the help of hydrogen peroxide, and the reaction is catalyzed by an enzyme called thyroid peroxidase (TPO).  Iodine is then incorporated into the tyrosine residues of a protein called thyroglobulin.  The combination of tyrosine and iodine helps to form the thyroid hormones.  Thyroxine (T4) contains four iodine atoms, whereas Triiodothyronine (T3) contains three iodine atoms.

However, tyrosine has other important roles as well.  For example, tyrosine is necessary for the formation of the neurotransmitter dopamine.  Tyrosine gets converted into l-dopa, which in turn gets converted into dopamine.  Dopamine in turn gets converted into norepinephrine and epinephrine.  As a result, a tyrosine deficiency can result in a decreased synthesis of these neurotransmitters.  Tyrosine is also necessary for the synthesis of CoQ10 (1) [1].

What Are Some Food Sources of Tyrosine?

Tyrosine is found in animal sources such as chicken, turkey, fish, and eggs.  It’s also found in other sources such as seaweed, avocados, and spinach.  Because it’s available in such a wide variety of foods, it is rare for people to be deficient in tyrosine.  In addition, the amino acid phenylalanine can be converted into tyrosine.  As a result, even if someone doesn’t eat a sufficient amount of foods rich in tyrosine, if they have adequate levels of phenylalanine then they most likely will have normal levels of tyrosine.

Should People With Hypothyroid Conditions Supplement With Tyrosine?

Since a tyrosine deficiency is rare, in most cases increasing one’s consumption of tyrosine and/or taking tyrosine supplements isn’t necessary.  After all, most cases of hypothyroidism are due to the autoimmune component of Hashimoto’s Thyroiditis, and are not caused by a tyrosine deficiency.  Therefore, in most cases it won’t be beneficial to take tyrosine supplements.  One of course can try to increase their consumption of tyrosine-rich foods, but once again, this will only help if someone has a tyrosine deficiency.

But how about those people with a non-autoimmune hypothyroid condition?  Even when someone has hypothyroidism without an autoimmune component, taking tyrosine usually won’t help.  The only situation where taking tyrosine will help is if someone has a deficiency of this amino acid.  So the next question you might have is “how can I determine if I have a tyrosine deficiency?”.  Even though having a tyrosine deficiency is rare, if you want to rule this out you can always do an amino acid profile, which not only will evaluate tyrosine, but the other amino acids as well.

In summary, tyrosine is a non-essential amino acid that is involved in the synthesis of thyroid hormone, as well as the neurotransmitters dopamine, epinephrine, and norepinephrine.  Even though tyrosine is necessary for the formation of thyroid hormone, most cases of hypothyroidism aren’t caused by a tyrosine deficiency.  Therefore, in most cases taking tyrosine supplements or increasing your consumption of tyrosine-rich foods won’t be beneficial.