The Phenylalanine/Tyrosine Ratio evaluates the body’s ability to convert phenylalanine to tyrosine; Conversion enzyme requires tetrahydrobiopterin (BH4), niacin (B3), and iron as cofactors.
Elevations in the serum Phenylalanine/Tyrosine Ratio have potential value for estimating the presence of an inflammatory disease and the catabolic state of a person.
This marker is also routinely used to screen newborns for phenylketonuria, an inborn error of metabolism that results in decreased metabolism of phenylalanine. This results in the buildup of dietary phenylalanine to potentially toxic levels. Not sufficient, because other causes of hyperphenylalaninemia (eg, BH4 deficiency) cannot be excluded by this test alone.
Phenylalanine is one of the amino acids, which are important nutrients that we get from our diets. Amino acids are used by the body to make protein which is essential for most physiological processes. Amino acids also serve as precursors to be converted by enzymes into other important compounds for the brain and other organs.
The metabolic pathway here is the conversion of phenylalanine into tyrosine. The importance of this pathway is that it removes excess phenylalanine and it enables the production of sufficient tyrosine. Tyrosine is important for the production of neurotransmitters that function in the brain. The enzyme phenylalanine hydroxylase (PAH) is responsible for enabling the phenylalanine to tyrosine conversion to take place.
Individuals with phenylketonuria have a genetic defect in the ability to produce PAH, therefore the phenylalanine they get from their diet keeps accumulating rather than being converted to tyrosine. The two major consequences are: (1) toxic levels of phenylalanine in the body and (2) high ratio of phenylalanine to tyrosine associated with impairment of the production of neurotransmitters.
High levels of phenylalanine, as seen in untreated phenylketonuria, cause brain damage and associated mental retardation. Early implementation of a low phenylalanine diet prevents the mental retardation associated with this condition.
Increased levels can potentially be used to diagnose phenylketonuria. If no inborn errors of metabolism (i.e. phenylketonuria) are present: Infections or inflammatory states often cause significant increases in serum phenylalanine and the phenylalanine-tyrosine ratio.
Own it for life
Our exclusive data entry service is a convenient way to get your results into your private dashboard. Simply attach an image or a file of your lab test results, and one of our qualified data entry team members will add the results for you. We support all sorts of files, whether PDFs, JPGs, or Excel. This service is excellent whether you have a lot of reports to upload or are too busy to do the data entry yourself.
We strive to make the data entry process easy for you. Whether by offering dozens of templates to choose from that pre-populate the most popular laboratory panels or by giving you instant feedback on the entered values. Our data entry forms are an easy, fast, and convenient way to enter the reports yourself. There is no limit on how many lab reports you can upload.
billed every month
Data entry included
$6.60/month billed annually
Data entry included
own it for life
Are You a Health Professional?
Get started with our professional plan
Welcome to Healthmatters Pro.
Save time on interpreting lab results with the largest database of biomarkers online. In-depth research on any test at your fingertips, all stored and tracked in one place. Learn more
Pro Monthly Plus
for health professionals
$75 per month