The essential amino acid phenylalanine breaks down to tyrosine. Tyrosine is used in the production of thyroid hormones, melatonin in skin, and the neurotransmitters, dopamine, norepinephrine, and epinephrine. These neurotransmitters are further broken down and excreted.
- Increased tyrosine may exacerbate migraine headaches and hyperthyroid conditions.
- Elevated tyrosine levels may occur due to supplementation (phenylalanine or tyrosine), heritable enzyme defects, or liver disease.
- High levels may indicate an inability to utilize tyrosine properly, perhaps because of low levels of enzyme co-factors such as iron, copper, iodine, B6, and vitamin C.
- Tyrosine is derived from dietary protein and, endogenously from the essential amino acid phenylalanine.
- Tyrosine is not only a constituent amino acid of proteins and enzymes but, importantly it is the precursor in the synthesis of dopa, dopamine, norepinephrine and epinephrine (adrenaline).
- Tyrosine is also iodinated to form the thyroid hormones. Hence a chronic deficiency of tyrosine can result in hypothyroidism, adrenal catacholamine deficiency and impaired neurotransmitter metabolism.
- Tyrosine deficiency can be associated with behavioral and learning disorders, depression, anxiety and inability to deal with stress, and symptoms commonly exhibited with hypothyroidism.
- Tyrosine has been used in the treatment and withdrawal of cocaine abuse.
- Low urinary tyrosine can result from phenylalanine deficiency, protein malnutrition or malabsorption, or impaired conversion of phenylalanine to tyrosine that may result in phenylketonurea.
- Whole food sources that are relatively high in tyrosine include meats, poultry, wheat germ, cottage and ricotta cheeses, soy protein, cashews and lentils. Most fruits, vegetables and cereals are low in tyrosine.
- Implicated in depression, hypothyroidism, blood pressure disorders. If phenylalanine is normal or high, iron, Vitamin C, and Niacin supplementation may help to convert phenylalanine to tyrosine.
- Low tyrosine relative to phenylalanine could also suggests that tetrahydrobiopterin (BH4) might be low.
Tyrosine, a nonessential amino acid, is high in this urine specimen. Tyrosine is derived from dietary protein and, endogenously from the essential amino acid phenylalanine. Tyrosine is a constituent amino acid of proteins and enzymes and, importantly it is the precursor in the synthesis of dopa, dopamine, norepinephrine and epinephrine (adrenaline). Tyrosine is also iodinated to form the thyroid hormones.
The conversion from tyrosine to dopamine, norepinephrine and epinephrine requires iron, copper, B-6, vitamin C and S-adenosylmethionine. A deficiency of B-6 or iron can result in elevated tyrosine. There are also various metabolic impairments in tyrosine metabolism that result from genetic aberrations that may cause increased levels of tyrosine in plasma as well as urine. If urine tyrosine is moderately elevated (500-1,000 micromoles/24 hr), retest after supplementation of B-6, vitamin C, and copper and iron (if these elements are low in whole blood or red blood cells). In addition, decreasing the intake of tyrosine and phenylalanine, and avoiding phenylalanine containing artificial sweeteners may help lower tyrosine levels and ameliorate symptoms. Whole foods that are relatively rich in tyrosine
and/or phenylalanine include peanuts, lentils, soy protein, tuna, anchovies, sardines, meats, poultry, wheat germ and cottage and ricotta cheeses.
Symptoms that may be associated with elevated tyrosine and impaired tyrosine metabolism include irritability, headaches, diarrhea, abdominal distension and failure to thrive and mental retardation in children.
An additional, yet less likely reason for elevated tyrosine is Hartnup Disorder, a renal amino acid retention disorder in which one would also see concomitant elevations in valine, leucine, isoleucine, phenylalanine, alanine and tryptophan.
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