title: The Ludwig pattern of androgenetic alopecia is due to a hierarchy of androgen sensitivity within follicular units that leads to selective miniaturization and a reduction in the number of terminal hairs per follicular unit.
abstract: BACKGROUND
  Hair follicles exist within follicular units (FUs). In utero the central primary hair follicles are surrounded by smaller secondary follicles. Each FU is nourished by a single arborizing arrector pili muscle that attaches circumferentially around the primary follicle with variable attachment to other follicles. Androgenetic alopecia (AA) miniaturizes susceptible scalp hair follicles in a distinctive and reproducible fashion manifesting in different patterns between men and women.
  
  
  OBJECTIVE
  We hypothesized that there is an additional layer to the patterning in AA, with a hierarchy of susceptibility within FUs to AA, and that the diffuse hair loss seen in women with AA is due to a reduction in the number of terminal hairs per FU rather than uniform miniaturization of entire FUs.
  
  
  METHODS
  We compared the mean numbers of FUs and terminal hairs per FU in 4-mm scalp punch biopsies in 24 women with AA with those in 21 controls.
  
  
  RESULTS
  There was no significant difference in the number of FUs; however, women with AA had 2.40 terminal hairs per FU compared with 3.38 in the control group (P=0.0001) associated with a mean increase of 0.6 vellus hairs per FU. Complete miniaturization of all hairs within the FU was not seen.
  
  
  CONCLUSIONS
  Diffuse hair loss in women with AA is due to a reduction in the number of terminal hairs per FU and an increase in the number of vellus hairs. This supports the hypothesis of a hierarchy of susceptibility within FUs to AA. Further investigation is required to ascertain whether secondary and tertiary hair follicles are more susceptible than primary follicles.
authors.affiliation: Department of Dermatology, St Vincent's Hospital, University of Melbourne, Fitzroy, Vic. 3065, Australia. yazdaa27@gmail.com
authors.forename: A
authors.initials: A
authors.lastname: Yazdabadi
authors.forename: J
authors.initials: J
authors.lastname: Magee
authors.forename: S
authors.initials: S
authors.lastname: Harrison
authors.forename: R
authors.initials: R
authors.lastname: Sinclair
mesh_terms: D000505:Alopecia / Q000209:etiology / Q000473:pathology*; D000728:Androgens / Q000502:physiology*; D001706:Biopsy; D005260:Female; D018859:Hair Follicle / Q000033:anatomy & histology* / Q000473:pathology; D006801:Humans; D012535:Scalp / Q000473:pathology
chemical_list: D000728:Androgens