HAIR CYCLE AND ALOPECIA

Male pattern alopecia is the outcome of profound modifications in the duration, succession and frequency of hair cycles. These phenomena wer e studied by phototrichogram in 10 male subjects, with or without alop ecia, over a period of 15 years. Almost 10,000 hair cycles were accoun ted for, yielding a detailed picture of the alopecia condition: (1) A decrease in the duration of anagen for a certain proportion of hairs, a proportion which increases in size, the more advanced the alopecia; the result of this premature transformation from anagen to telogen is an increase in the rate of hair loss. (2) A parallel decline in hair d iameter. (3) Longer latency periods between the fall of a hair and the onset of regrowth, leading to a reduction in the number of hairs pres ent on the scalp surface. The shorter finer hairs are absent more freq uently and absent for longer periods and this contributes to the effec t of alopecia.