Hair Diameter vs. Hair Density in Male Androgenetic Alopecia

A study evaluated over 300 Japanese males with or without androgenetic alopecia (AGA) using a videomicroscopic technique and found that vertex hair density did not decrease with balding, whereas the thickness of vertex hair decreased significantly. Therefore, hair loss is attributable to gradual miniaturization of hair follicles that results from the transformation of terminal hairs into vellus hairs, rather than to increased hair shedding. The study suggests that the change in hair diameter serves as a reliable indicator of progression and therapeutic effects in male AGA. The study also notes that medications like topical minoxidil, oral finasteride, and dutasteride can improve hair regrowth and increase hair thickness, but they are unlikely to increase the total hair number if the density of vertex hair remains constant during the progression of balding.