Hair follicle miniaturization is a process whereby a hair strand gets thinner over time. Hair follicle miniaturization is used in the diagnosis of hair loss disorders such as androgenic alopecia (AGA), also known as male pattern hair loss and female pattern hair loss. Hair follicle miniaturization is also seen in some scarring alopecias, as well as alopecia areata. However, the way in miniaturization advances tends to differ across hair loss disorders:
- Androgenic alopecia: each hair strand tends to miniaturize in between hair cycles. Moreover, hair diameter diversity is often present (i.e., some shedding hairs appear thick, while others appear thin). Sebaceous glands remain intact.
- Scarring alopecias: hair follicle miniaturization often occurs alongside the destruction of the sebaceous gland.
- Alopecia areata: hair follicle miniaturization may occur uniformly across all affected hair follicles. Moreover, hair follicle miniaturization can happen during the same hair cycle, leading to "exclamation-mark hairs" whereby the tip of the hair is thicker than the root of the same hair (i.e., active miniaturization). This is unique from androgenic alopecia, where hair strand thickness remains mostly constant throughout the entire hair growth cycle.