🔑 Core Function

• Neurotransmitter precursor: Converts to dopamine → norepinephrine → epinephrine (adrenaline).
• Thyroid hormone synthesis: Required for thyroxine (T4) and triiodothyronine (T3).
• Pigment formation: Needed for melanin → skin, hair, and eye colour.
• Protein structure: Incorporated into enzymes and receptors; phosphorylation site for signalling.

🧬 Family & Essentiality

🌿 Plain-Language Summary

Tyrosine is the body’s “brain & hormone builder” ⚡. It helps make dopamine (motivation), adrenaline (energy), thyroid hormones (metabolism), and melanin (pigment). Normally made from phenylalanine, it becomes especially important when demand is high.

⚗️ Molecular & Chemical IDs

• Abbreviation: Tyr / Y
• Chemical formula: C₉H₁₁NO₃
• Structure: Aromatic hydroxylated phenylalanine derivative

⚡ Functions

• Brain chemistry: Dopamine, norepinephrine, epinephrine synthesis.
• Endocrine health: Thyroid hormone backbone (iodination of tyrosine in thyroglobulin).
• Pigmentation: Melanin production in skin, eyes, hair.
• Cell signalling: Tyrosine phosphorylation regulates enzyme and receptor activity.

🍽️ Absorption & Bioavailability

🇦🇺 Australian NRVs (NHMRC)

• EAR: ~16 mg/kg/day (phenylalanine + tyrosine combined)
• RDI: ~22 mg/kg/day (phenylalanine + tyrosine combined)
• Source: NHMRC / FAO / WHO requirement values

🥗 Food Sources

• Meat, poultry, fish
• Dairy (milk, yoghurt, cheese)
• Eggs
• Soy products, legumes, nuts, seeds, whole grains

With adequate protein intake, tyrosine needs are usually met.

🧪 Testing & Monitoring

• Plasma amino acid profiling (specialist labs).
• Measured in newborn screening for phenylketonuria (PKU).
• ❌ Not a standard GP test in adults unless a metabolic disorder is suspected.

🔄 Interactions

• ➕ Requires vitamin B6, iron, and copper for dopamine synthesis.
• ➕ Iodine needed for thyroid hormone production from tyrosine.
• ⚠️ PKU: Phenylalanine → tyrosine conversion impaired; tyrosine becomes essential.
• ⚠️ High-dose supplementation may interact with thyroid medicines or MAOIs.

📊 Evidence Snapshot

• ✅ Established: Core precursor for neurotransmitters, thyroid hormones, and melanin.
• ⚖️ Contextual: Supplemental tyrosine studied for stress, fatigue, and cognition — evidence mixed; benefits most likely under acute stress or sleep deprivation.