Follistatin is a protein made naturally in the body. It binds to and blocks members of the TGF-β family of signalling proteins, particularly activin.

Some cosmetic products list an ingredient called sh-Polypeptide-86, which suppliers describe as a lab-made form of human follistatin. No published clinical trial has tested a topical product containing it for hair loss.

What lab and animal studies show

The hair follicle cycles through growth (anagen) and rest (telogen) phases. Members of the TGF-β family, such as activin and bone morphogenetic proteins (BMPs), are involved in controlling this cycle.

A 2003 mouse study found that mice lacking follistatin showed slower hair follicle development, and that adding follistatin protein to embryonic mouse skin in a dish stimulated follicle development (Nakamura et al. 2003, FASEB J, PMID 12514121). The authors concluded that the balance between follistatin and activin plays a role in follicle development and cycling. This is mouse developmental biology. It does not show that follistatin regrows hair in people.

Human evidence

The only human hair study involving follistatin is a small Phase 1 trial run by the product's maker, Histogen (Zimber et al. 2011, J Drugs Dermatol, PMID 22052313). Twenty-six men with androgenetic alopecia received a single injection into the scalp of a cell-derived mixture called Hair Stimulating Complex (HSC). HSC contained follistatin together with other growth factors (KGF and VEGF) and showed Wnt activity.

The authors reported that, at 12 weeks, treated sites had greater increases in hair shaft thickness and terminal hair density than placebo sites, and that total hair count was still higher at one year. All 26 participants tolerated the injection and no adverse reactions were reported over 52 weeks.

The study was small, was run by the product's maker, and tested a mixture. It cannot show what follistatin alone does, and it was too small to rule out uncommon side effects. It has not been followed by published larger trials.

Safety and regulatory status

Follistatin's safety as a hair treatment is unknown. It is not an approved medicine for hair loss in any country we are aware of. Injectable or "research peptide" follistatin products, and follistatin gene therapies offered outside regulated clinical trials, are of unknown content and safety.

For topical products, a further question is delivery. Follistatin is a large protein, and it has not been shown that it can pass through the skin to reach the hair follicle.