sh-Polypeptide-9 for Hair Regrowth - Quick Reference Sheet

sh-Polypeptide-9 for Hair Regrowth

Created on 08/02/2026 – Quick Reference based on Evidence Review created using AI4L / Opus 4.8 Audit

A lab-made copy of a natural blood-vessel-building protein, applied as a scalp serum for thinning hair. The rationale is sound and animal and cell studies show larger follicles and faster regrowth, but no human study has tested it alone, and getting the large protein into skin is hard. Everyday risk is low; proof of regrowth remains thin. (Full Review)

Protocol

Application
Leave-on serum
To clean, dry scalp over thinning areas; massaged in
Frequency
1–2× daily
Twice-daily split application more common; used continuously
Delivery
Often with microneedling
Commonly paired with microneedling to aid delivery
Time to effect
Visible change
3–6 months
Consistent use before assessing; matches the hair cycle

Benefits

Contraindications
  • Current or recent melanoma or other active malignancy
  • Active scalp infection, open lesions, or uncontrolled inflammatory scalp disease
  • Pregnancy or breastfeeding
Key Interactions
  • Topical minoxidil
  • Other topical growth-factor or peptide serums (epidermal growth factor, fibroblast growth factor)
  • Topical retinoids and chemical exfoliants (retinoic acid, glycolic/salicylic acids)
  • Microneedling and other barrier-disrupting procedures
  • Oral anticoagulants and antiplatelet agents (warfarin, apixaban, aspirin, clopidogrel)

Risk & Side Effects

  • High:
  • Medium:
  • Low: Application-site irritation and contact dermatitis
  • Speculative: Theoretical tumor-angiogenesis concern with systemic absorption; recombinant-peptide immunogenicity or hypersensitivity; unknown long-term safety and absent regulatory oversight

Monitoring

Marker Target Why
Ferritin ~40–70 ng/mL Low iron stores independently cause and worsen hair shedding
Vitamin D (25-hydroxyvitamin D) ~40–60 ng/mL Low vitamin D is associated with hair thinning and poorer follicle cycling
Thyroid-stimulating hormone (TSH) ~0.5–2.5 mIU/L Both under- and over-active thyroid cause diffuse hair loss and mimic other alopecias
Total and free testosterone / DHT (selected cases) Age- and sex-appropriate Androgen excess drives pattern loss the serum cannot counter

Cadence: Standardized photographs at baseline, then ~3 and 6 months, and roughly every 6 months thereafter; repeat labs only if a deficiency was found

Qualitative Assessment

  • Reduced daily shedding (hairs on pillow, in the shower, on the brush)
  • Subjective scalp coverage and part-width when styling
  • Emergence of finer regrowth hairs along the hairline or part
  • Scalp comfort and tolerability (absence of persistent irritation)