Laboratory-made thymosin beta-4 listed in hair serums. Animals grew hair faster; no trial counted hairs for it alone. Only human scalp study of it alone improved flaking, not hair counts. Clinic blends report thicker-looking hair. Human hair grown outside the body grew slightly less. Vessel growth is a longer-range concern. Whether the product matches the label is an evidence problem. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Hair density (phototrichogram) | Change from own baseline; non-thinning vertex often about 150–250 hairs/cm² | Detects conversion to visible terminal hair |
| Shaft diameter | Increase versus that person's baseline | Tracks miniaturization, the androgenetic endpoint |
| Hair-pull test | Negative or clearly improved versus baseline | Simple shedding check |
| Adherent flaking / erythema | Return toward that person's pre-flare state | Captures seborrheic benefit seen with the 0.5 mg/ml gel |
| Ferritin | Often targeted ≥70–100 ng/mL in longevity-oriented hair work | Rules out a common alternative cause of shedding |
| TSH | Typically 0.5–2.5 mIU/L in functional practice | Hypothyroidism mimics telogen shedding |
Cadence: Baseline, then 4 weeks (isolated-gel window), 12 weeks, then every 3–6 months if use continues