A study of female pattern hair loss

© 2013 Dr. Anousha YazdabadiA full head of luscious hair is a very desirable trait for humans and loss of this hair which is a common problem is a devastating affliction, particularly for females. Apart from its cosmetic and social significance the human hair follicle forms an intricate anatomical structure called the follicular unit consisting of a combination of terminal and vellus hairs as well as an arborising arrector pili muscle and sebaceous gland. The importance of this anatomical structure and its individual components in maintaining human hair growth is increasingly being realised. The main emphasis of this thesis is the study of this remarkable micro-anatomical unit in hair loss disorders. After establishing that individual hairs are lost from follicular units rather than entire follicular units in female pattern hair loss, possibly due to a hierarchy of susceptibility to miniaturization within follicular units, the research comprising this thesis then goes on to explore the potential role of the arrector pili muscle in this process. In fact it appears that loss of attachment of this microscopic muscle to the bulge of miniaturized hair follicles which are a repository of stem cells, equates to an inability to reverse hair follicle miniaturization as seen in female and male pattern hair loss. On the other hand when the arrector pili muscle maintains its attachment to the bulge of the miniaturized follicle as seen in alopecia areata, there is a potential for complete reversibility of the miniaturization process. Thus the attachment of the arrector pili muscle to the bulge is more than just by chance and the arrector pili muscle is likely to be more than just a vestigial muscle of piloerection. Furthermore it seems that the follicular unit is a dynamic structure showing further development post-partum with increasing numbers of total hairs as well as increasing proportions of two, three and four haired follicular units in adulthood compared to infancy. The composition of follicular units in female pattern hair loss however more closely resembles that of the infant with a larger proportion of single haired follicular units than the adult unaffected by hair loss. The research contained within this thesis has led to the development of a new model for the pathogenesis of female pattern hair loss in which the follicular units, in particular the arrector pili muscle play an important role in the pathophysiology of hair loss disorders