Figure 1. Miniaturisation of the hair follicle.

In a previous F1000 article, a model of androgenetic alopecia is presented¹¹. Through consecutive hair cycles, progressive miniaturisation of the hair follicle unit occurs, initially affecting secondary follicles, associated with hair density reduction, before the arrector pili muscle is replaced by fat³². Ultimately, detachment of this muscle from the regenerative bulge area is associated with irreversible hair loss^11,32. This figure was adapted from Sinclair et al.¹¹ which is licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) (https://creativecommons.org/licenses/by-nc/4.0/).