The Human Hair Follicle Has Established a Fully Functional Peripheral Equivalent of the Hypothalamic-Pituitary-Adrenal Axis (HPA)

The study demonstrated that human hair follicles possess a fully functional peripheral equivalent of the hypothalamic-pituitary-adrenal (HPA) axis. Researchers found that stimulating organ-cultured human scalp hair follicles with corticotropin-releasing hormone (CRH) or adrenocorticotropic hormone (ACTH) led to significant upregulation of proopiomelanocortin (POMC) transcription and increased immunoreactivity of hormones such as alpha-MSH, ACTH, and cortisol. This indicated that hair follicles could synthesize cortisol, an "adrenal" steroid hormone, and that this synthesis was regulated by the same hormones controlling adrenal cortisol production. The findings suggested that hair follicles could coordinate stress responses and integrate them into metabolic and neuro-endocrine-immune signaling, which could have implications for skin physiology and dermatological therapy.