Miniaturisation

Miniaturisation is what pattern hair loss actually is. In genetically susceptible follicles, ongoing DHT exposure shortens each anagen growth phase and progressively reduces follicle size.

The visible result over years: each new hair from the affected follicle is a little thinner, a little shorter, and a little less pigmented than the last. Thick terminal hairs are gradually replaced by thinner intermediate hairs, then by fine vellus-like hairs, then nothing.

The follicle itself is not destroyed. This is why DHT blockers (finasteride, dutasteride) and minoxidil can partly reverse miniaturisation in early stages. A follicle that has not produced terminal hair for 5 to 10 years has limited capacity to be revived.

Miniaturisation is visible on trichoscopy as variability in hair shaft diameter within a small scalp area. It is the diagnostic signature of androgenetic alopecia.