L-Tyrosine, a common dietary amino acid sold as a supplement for mental performance, looks like a situational tool, not a proven longevity aid: a single dose before demanding or stressful situations appears to help protect short-term memory and attention, with small, task-specific gains. In older adults, higher doses were linked to worse performance on hard memory tasks. Short-term use at common doses was well tolerated; daily use remains uncertain. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Thyroid-stimulating hormone (TSH) | 0.4–4.0 mIU/L | Safety check: a falling value stops or changes use |
| Free thyroxine (free T4) | 0.8–1.8 ng/dL | Safety check: a rising value stops use |
| Plasma tyrosine (plasma amino acid panel) | 34–112 µmol/L; track change from own baseline | Expected to change: confirms intake and absorption |
| Blood pressure (home checks) | No target range given | When combining with other stimulating compounds |
Cadence: Common practice is a thyroid panel (TSH and free T4) at baseline; for daily use, typically repeated at 4–8 weeks, then every 6–12 months; occasional users typically retested only if symptoms arise; home blood-pressure checks during the first week of combined use.