Hair Transplantation: Biochemical Basis and Surgical Treatment

Modern day hair transplantation has undergone tremendous advances since the understanding of the patterns of male hair loss and miniaturization related to androgenic alopecia caused by DHT (dihydrotesterone).  The concept of donor dominance, in which hairs genetically resistant to the effects of DHT can be moved to other locations where hair has been lost due to sensitivity to this hormone, is the basis for modern day hair transplantation.  Early hair transplantation based on this knowledge involved moving plugs of hair from DHT resistant hairs posteriorly to the anterior hairline.  These however resulted in abnormal hairlines which did not appear natural.  Presently, hair transplantation is placed on the use of 1, 2, 3, and 4 hair follicular units to create more natural hairlines.  In addition, knowledge of the biochemistry of hair loss has resulted in nonsurgical treatments that can regrow and maintain hair.  Finasteride (Propecia) and minoxidil (Rogaine) are now important adjuncts before, during and after hair transplantation.  Advances have been made in the harvesting of donor hair including the use of follicular unit extraction which removes individual 1, 2, 3 or 4 hair follicular units and the use of robots for extraction.  Because of the limitations of donor sites and the fact that hair loss is progressive, future research will involve the use of stem cells. This review contains 27 figures and 106 references. Key Words: androgenic alopecia, cicatricial alopecia, DHT, donor dominance, follicular units, miniaturization, stem cells, telogen effluvium, trichophytic