Injectable botulinum toxin (BT) may have potential as a treatment for patients with androgenetic alopecia (AGA), researchers suggested in a commentary published in the Journal of Cosmetic Dermatology.
AGA is the most common form of alopecia, but the only FDA-approved treatments for the disorder are topical minoxidil in women and topical minoxidil and oral finasteride in men. However, recent research has suggested that injectable BT may be a possible adjuvant treatment for patients with the disorder.
Alteration of androgen sensitivity and genetic predisposition are important factors in the etiopathogenesis of the disease, and oxidative stress and perifollicular microinflammation are also contributing factors. In AGA, bald areas have lower oxygen levels than nonbald areas, the investigators recounted. Because conversion of testosterone to dihydrotestosterone (DHT) occurs in an environment with low oxygen levels, an increase in blood supply would reduce local hypoxia and could be beneficial in AGA, suggested the investigators.
DHT induces production of transforming growth factor-β1 (TGF-β1) in the cells of the dermal papilla. TGF-β1 has a relevant role in the onset of AGA, and antagonizing it could prevent disease progression, according to the researchers.
The rationale for using BT in patients with AGA would be to promote relaxation of the scalp muscles, which would reduce muscle pressure on perforating vessels and potentially increase blood and oxygen flow to bald areas, noted the investigators.
“Therefore, there would be a reduction in tissue DHT due to the effect known as ‘wash out,’ and consequently, less follicular miniaturization would occur, which is considered the main pathophysiological basis of this disease,” the researchers noted.
As men with AGA have been shown to have significantly greater stiffness at the apex of the scalp compared with other areas, this stiffness could be related to fibrosis promoted by increased levels of TGF-β1 in the sites affected by the disease. Thus, BT injection could inhibit TGF-β1 secretion from hair follicles, leading to an antifibrotic effect.
“As other complementary etiopathogenic mechanisms emerge, new hypotheses arise to complement already approved classic therapies,” the researchers commented. “In this sense, injectable BT seems to have a theoretical rationale that supports its use in order to expand the therapeutic arsenal for AGA, although robust clinical trials are needed to validate whether the rationale for its use is confirmed in clinical practice.”
Melo DF, Ramos PM, Antelo DAP, Machado CJ, barcaui CB. Is there a rationale for the use of botulinum toxin in the treatment of androgenetic alopecia? J Cosmet Dermatol. Published online April 24, 2021. doi: 10.1111/jocd.14177