Hair through the female life cycle.

At a population level female scalp hair growth shows features of regression with chronological ageing, although there is wide interindividual variation in timing and degree. The subjective assessment of hair loss is classically determined by hair density but it is apparent that other factors contribute to the clinical picture. Changes can occur in hair cycling, hair density, hair diameter and pigmentation, and possibly in structural qualities of the hair fibre. These changes are most pronounced in female pattern hair loss. Although conventionally considered as the female counterpart of male androgenetic alopecia the evidence that female pattern hair loss is androgen dependent is less clear cut than in men and it probably has a multifactorial basis. The emerging evidence implicating environmental factors is of particular interest as, unlike genes, such factors may be amenable to intervention. The clinical signs in women complaining of hair loss may be variable. In evaluating the patient complaining of hair loss, while true pathology must always be considered, the clinician needs to be aware of how age affects hair growth. These changes form the focus of this article.