The Higher Number and Longer Duration of Kenogen Hairs Are the Main Cause of the Hair Rarefaction in Androgenetic Alopecia.

The progressive reduction of the number of terminal hairs and the simultaneous increase in the number of vellus hairs (hair miniaturization) are the current explanation of human baldness. In a 2.5-year study on 43 male subjects with androgenetic alopecia (AGA), we found that oral finasteride augmented the total number of hairs by 55%, but failed to decrease the prevalence of vellus hairs. While our data may explain why, in AGA, hairs become progressively softer and combable, they cannot explain why areas of hair rarefaction develop. We propose that the longer duration and higher frequency of kenogen hairs are the real mechanism through which the scalp hairs rarefy.