Clinical Research Center for Hair and Skin Science

In the project funded by the Innovation Committee at the G-BA, the S3 guideline for the diagnosis and treatment of AA was developed between 2023 and 2025. The interdisciplinary expert panel consisted of representatives from the German Dermatological Society, in particular from the Pediatric Dermatology Working Group, the Professional Association of German Dermatologists, the German Society for Psychosomatic Medicine and Psychotherapy, the German Society for Pediatrics and Adolescent Medicine, the Austrian Society for Dermatology and Venereology, a hairdresser as an external consultant and two patient representatives. In the first of two parts, we present the key statements on epidemiology and the recommendations for diagnosis. Data from Germany show a population-based prevalence of AA of 0.22% (95%CI 0.21-0.22) for 2016 and 0.21% (95%CI 0.20-0.22) for 2020. This means that 170,000 people in Germany were diagnosed with alopecia areata (AA) in 2020. International data show a pooled prevalence of 2.1%, but with large regional differences. Data on the incidence of AA from Germany show that 72 patients per 100,000 were newly diagnosed with AA in 2020 (RR 0.072%; 95%CI 0.07-0.08). Extrapolated to the German population, this means that around 70,000 people were newly diagnosed with AA in 2020.

Abstract We have previously shown that the thyroid hormones triiodothyronine (T3) and thyroxine (T4) prolong anagen, mitigate stem cell apoptosis, and stimulate mitochondrial functions in microdissected human scalp HFs ex vivo. To circumvent the systemic adverse effects of T3/T4, we have asked in the current pilot study whether topically applied T3/T4 retains hair growth-promoting properties. To prove this, we have topically treated healthy full-thickness human scalp skin with T3 (1, 10nM) and T4 (1, 10μM) for six days in serum-free organ culture, using an HF-targeting vehicle that contains only FDA-approved ingredients. This showed that, at distinct doses, topical T3 and T4 significantly increased the percentage of HFs in anagen, decreased the percentage of proliferative (Ki-67+) cells in the hair matrix, did not promote melanogenesis (as measured by quantitative Warthin-Starry histochemistry), and significantly increased keratin 15 expression in the bulge. Finally, T3 and T4, at low concentrations, increase the expression of the hair growth promoters IGF-1 and FGF-7. The lower concentration of T3 and both of T4 also significantly increases the number of CD31+ endothelial cells, suggesting a pro-angiogenic effect, which is also important for hair growth promotion. These preliminary results strongly suggest that topically applied thyroid hormones promote hair growth in intact human scalp on multiple levels ex vivo. This invites the intermittent pulse application of topical T3 and T4 as a novel therapeutic intervention for managing hair loss disorders associated with telogen effluvium, such as androgenetic alopecia.