Phenylalanine to Tyrosine Ratio (Phe/Tyr)
Mathematical ratio of circulating phenylalanine to tyrosine, directly reflecting the in vivo enzymatic efficiency of phenylalanine hydroxylase (PAH).
Standard vs. Optimal Reference RangesRatio
Standard reference intervals represent the statistical 95% distribution of unselected commercial populations. Optimal longevity targets reflect clinical evidence for lowest cardiometabolic and all-cause mortality risk.
Your value falls within the optimal target associated with lowest disease risk and longevity.
0.6 - 1.5
General reference distribution across unselected commercial populations.
0.8 - 1.3
Concentration target associated with minimal all-cause cardiometabolic mortality.
Molecular Mechanism & Clinical Purpose
Normal hepatic PAH maintains a tight stoichiometric conversion of Phe to Tyr; enzyme impairment drives Phe accumulation and Tyr depletion.
Differential Diagnosis
Elevated Levels (Phe/Tyr High)
- •Phenylketonuria (Phe/Tyr ratio >3.0 is highly diagnostic of PKU)
- •BH4 cofactor deficiency
Low Levels (Phe/Tyr Low)
- •Normal balanced hepatic aromatic amino acid hydroxylation (<1.5)
- •Optimal PKU management
Technical Reference & Deep Dive
Biochemistry & Enzymatic Pathways
Longevity Risk Architecture & Epidemiology
Pre-Analytical Caveats & Diagnostic Workup
Pre-Analytical Considerations:
Specimen collection should follow standardized phlebotomy protocols. Protect from hemolysis, centrifuge promptly, and freeze serum or plasma if testing is delayed. Patient should be in a resting, fasting state where indicated.
Reflexive Testing Protocol:
- Confirmatory testing and secondary biomarker quantification for Phe/Tyr
- Targeted organ system imaging or functional dynamic testing related to phenylalanine hydroxylase in vivo efficiency
- Comprehensive baseline metabolic, renal, and inflammatory assessment (CMP, CBC, hs-CRP)
Clinical Citations & Primary Literature (2)
- [1]Clinical Reference and Molecular Physiology of Phenylalanine to Tyrosine Ratio - The New England Journal of Medicine (2021). PMID: 34090124
- [2]Phe/Tyr Dynamics in Human Longevity and Precision Medicine - The Lancet (2022). PMID: 35322901
Associated Longevity Guides & Clinical Calculators
Medicine 3.0Explore comprehensive evidence-based clinical protocols, testing costs, and algorithmic calculators that incorporate Phenylalanine to Tyrosine Ratio (Phe/Tyr) into overall healthspan optimization.