Local Actions of Thyrotropin-Releasing Hormone Regulate Hair Color

The study by Gáspár and colleagues in 2011 explored the role of thyrotropin-releasing hormone (TRH) in human hair pigmentation. They discovered that TRH is produced in human scalp hair follicles and stimulates melanin production specifically in these follicles, but not in epidermal melanocytes. This effect is independent of the pituitary gland and involves the melanocortin-1 receptor and possibly proopiomelanocortin. These findings suggested a novel pathway for hair pigmentation and potential therapeutic interventions for hair graying. The research primarily used organ-cultured human hair follicles to demonstrate these effects.