[Hair growth promoters in androgenetic alopecia. Expectations and reality]

Androgenetic hair loss is the most frequent reason for the topical application of hair-growth-promoting agents. Such preparations should arrest or even reverse androgen-induced hair follicle regression as well as prolonging the hair cycles, especially of the shortened anagen phase, and thus protect from increased hair loss. True evidence of drug effects on hair growth is problematic, since trichograms, the method chiefly applied by the manufacturers, fail to reveal every factor involved in the follicular activity, especially the duration of anagen stage. For example, an increase in the anagen rate does not always reflect a lengthening of the anagen stage, but may also be due to shortened hair cycles. Accordingly, drug effects on hair growth should be investigated by methods that analyse the cell cycle kinetics. For this approach DNA-flowcytometry of the outer root sheath in plucked anagen hairs and of complete anagen hair bulbs taken by micropreparative techniques from scalp biopsies offers a reproducible method for quick and reliable evaluation of hair growth.