Avaliação da eficácia terapêutica da toxina botulínica na alopecia androgenética masculina

Abstract

Androgenetic alopecia (AGA) is the most common form of alopecia in men. It is a chronic, progressive condition that results in a decline in the metabolic activities of the hair follicle. Terminal hairs are converted to thin hairs (vellus). AGA can compromise the self-esteem and quality-of-life of affected individuals. Currently, only topical minoxidil and oral finasteride and dutasteride are approved to treat male AGA. Altered androgen activity and genetic predisposition are fundamental in the development of the disease. Hair follicles become more susceptible to the conversion of testosterone to dihydrotestosterone (DHT) in peripheral tissue. Oxidative stress, perifollicular microinflammation and microvascular insufficiency have been identified as triggers. Oxidative stress alters the morphology, proliferation and apoptosis of dermal papilla cells. Activation of T lymphocytes by exogenous stimuli such as UV radiation, pollutants and alteration of the microbiome explains microinflammation. It is known that bald areas have a certain degree of microvascular insufficiency, with lower oxygen levels than non-bald areas. The conversion of testosterone to DHT occurs in a hypoxic environment and, therefore, greater blood supply may be beneficial in the treatment of AGA. Botulinum toxin (BT) is a neurotoxin obtained from C. botulinum, which inhibits muscle contraction by blocking acetylcholine. It has wide medical, aesthetic and therapeutic uses such as in hyperhidrosis, strabismus and neurology. In AGA, its injectable use would promote relaxation of the scalp muscles, increased blood flow to the bald areas, reduction of TGF-β (pro-apoptotic) tissue DHT and follicular miniaturization. The objective of this study was to evaluate the efficacy of BT as a therapeutic option in male AGA. It was carried out in the dermatology department of HUPE. Thirteen men aged 18 to 45 years, with AGA for less than 10 years and without treatment, were included in the study. This was a triple-blind, self-controlled, randomized clinical trial. One side of the scalp received 50 IU of BT (5 IU/point; 10 points) at week zero and week 12. The contralateral area received 10 saline punctures. Clinical and trichoscopic photographs were taken at weeks 0, 12, and 24. The efficacy of BT was assessed by trichoscopy, a valuable tool in the evaluation of several scalp diseases. The matching technology (TrichoLAB® hair-to-hair matching technology) ensured that images were compared at the same exact site. Median comparisons were made between the sides of the scalp at the three visits and on each side over time, based on parameters of total density, hair thickness, and total new hair growth on both scalp sides. The nonparametric Wilcoxon test for paired samples was used. The estimated level of statistical significance was 5%. In our study, BT did not promote hair growth in men with AGA after 12 or 24 weeks. Frontal and vertex hair density decreased on both sides (BT and placebo) and an increase in the vellus/terminal ratio occurred. In conclusion, our study found no benefit of injectable BT for male AGA using an accurate and objective hair counting technology.