What is Tyrosine?

In anyone who does not have PKU. Phenylalanine is broken down by the enzyme we don’t have and is converted to Tyrosine. Tyrosine is an amino acid. Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid ( Source Wikapedia) https://en.wikipedia.org/wiki/Tyrosine.

Tyrosine is incorporated into all proteins and is a precursor of thyroxine, melanin, and the neurotransmitters dopamine and norepinephrine.. ( source : The American Journal of Nutrition)

Tyrosine is found in foods with high amounts of Phenylalanine such as meat, dairy, seeds, soy , beans, avocados, and bananas.

As someone with PKU I do not produce tyrosine .

What does Tyrosine do?

A number of studies have found tyrosine to be useful during conditions of stress, cold, fatigue, prolonged work and sleep deprivation, with reductions in stress hormone levels  and improvements in cognitive and physical performance .  ( Source Wikapedia)

Tyrosine and Maternal PKU

Occasionally in pregnant women with PKU , tyrosine is added to formula for growth and development of the fetus. Having PKU limits the amount of tyrosine in my body and We do not get enough from our formula and low protein diet to accommodate pregnancy. If you have PKU and are not pregnant you do not need to supplement.  For PKU pregnancy Tyrosine is recommended to be between 33 and 61 in the second trimester.

Tyrosine levels fluctuate during the day and fasting vs non fasting that is why there is a range.  During the first trimester I did not require supplementation.  Now as I progress through 2nd trimester I am having to add tyrosine powder to my formula.  I started off with 5 grams daily divided up between the day. Then my levels dropped again. My clinic does not make the decision to change my tyrosine supplementation or phe tolerance based on one level so we wait to see one or 2 more before increasing. I am now up to 8 grams of tyrosine a day and my last phe level was 2.7 and tyrosine 47. Both perfectly in range.  We expect to increase my phe and tyrosine dosage again soon. Specially in 3rd trimester.

Low tyrosine and low blood phe levels can cause slow growth or growth retardation, So Raising tyrosine concentrations in blood may increase the amount of tyrosine and decrease the amount of phenylalanine transported across the blood-brain barrier. So this is beneficial to the PKU brain and developing baby.

Essentially, because I don’t have enough Tyrosine in my body due to my PKU, neither does the baby. The baby needs the tyrosine to grow. I cannot provide it from the foods I eat.  Though I get enough for myself in my formula. I need extra to sustain a growing fetus.  Tyrosine crossed the placenta at a high rate then what is used and needed in my body. So when my blood phe levels are tested we are also looking at tyrosine to monitor levels and insure its not to low or not to high. High tyrosine levels can also be toxic.

Side effects of high levels of Tyrosine is not yet well known.

I am currently researching this topic and have sent a request to my clinic to further provide education and information for you. I hope this post has been helpful and I hope to expand on it again in the near future.