The Hair Follicle as an Estrogen Target and Source

The document from 2006 explores the complex role of estrogens and estrogen receptors (ERs) in hair follicle biology, emphasizing their significant influence on hair growth and cycling. It reveals that estrogens act on hair follicles by binding to ERs, which are present in various hair follicle compartments and vary in expression during different hair cycle stages. The paper notes that estrogens can modify androgen metabolism within the hair follicle, potentially affecting hair growth disorders such as androgenetic alopecia, hirsutism, telogen effluvium, and chemotherapy-induced alopecia. The document also discusses the importance of understanding the sex-dependent and site-dependent differences in hair follicle responses to estrogens, as well as the interplay between estrogen signaling and other growth factors and pathways. It suggests that estrogens may act as a hair cycle brake, particularly by maintaining the telogen phase, and highlights the need for more research to fully understand the mechanisms of estrogen action in hair biology and to develop targeted treatments for hair loss conditions.