A lab-made copy of the protein follistatin, added to scalp serums to block signals that keep hair follicles resting. The underlying biology is well supported in animal studies, but the only human evidence used an injected mixture, not a topical serum. Whether the large protein even reaches follicles from a serum is unresolved. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Ferritin (iron stores) | 40–70 ng/mL | Low iron stores are a common, correctable cause of shedding that can mask any benefit |
| Vitamin D, 25-hydroxy (25-OH-D) | 40–60 ng/mL | Low vitamin D is associated with hair shedding and follicle cycling problems |
| Thyroid-stimulating hormone (TSH) | 0.5–2.5 mIU/L | Both under- and over-active thyroid cause diffuse hair loss that mimics or masks pattern loss |
| Total and free testosterone | Mid-normal for age and sex | Helps contextualize androgen-driven loss, which a follistatin serum does not address |
| Dihydrotestosterone (DHT) | Sex-appropriate reference | The main androgen driving follicle miniaturization; frames whether a DHT-directed therapy is also needed |
Cadence: Photos at 3 and 6 months, then every 6 months; repeat blood markers only if baseline values were abnormal or symptoms change