Androgenic alopecia causes the hair follicle to be unable to survive on the scalp. This is because the hair follicle decreases in size, eventually disappearing entirely and, therefore, the hair.
Dihydrotestosterone (DHT) is the hormone that weakens the hair follicles on the top of the head. Therefore, it is what favors the development of the typical characteristics of hair affected by androgenic alopecia. At some point, even though the hair follicle is still alive and remains on the scalp, due to its miniaturization, the hair stops growing.