Current Understanding of Androgenetic Alopecia: Part I - Etiopathogenesis

Androgenetic alopecia (AGA) was identified as the most common form of hair loss in both men and women, characterized by a specific pattern in genetically predisposed individuals. The genetic basis was not fully understood, but evidence suggested a polygenic rather than a simple Mendelian trait. AGA was defined as a dihydrotestosterone (DHT)-dependent process, involving the miniaturization of hair follicles. The molecular mechanisms distinguishing androgen-dependent beard growth from hair loss in AGA were unclear. However, advances in research highlighted the role of steroidogenic isoenzymes, particularly type 2 5α-reductase in the dermal papilla, which facilitated the conversion of testosterone to DHT, playing a central role in the pathogenesis of AGA.