Aetiology and pathophysiology of hair loss.

The prevalence of androgenetic alopecia has not been accurately recorded but it is probably true that, at least in caucasoid races, some degree of transformation of terminal to vellus hair follicles on the vertex from puberty onwards is a universal phenomenon in both sexes, although androgenetic alopecia in women more often assumes a diffuse form. Our knowledge of the pathogenesis of ordinary baldness is far from complete but a genetic predisposition is necessary and androgen production must be present. In general it can be concluded that whatever the level of circulating androgens, free or total, the major genetic factor must reside in the end-organ response- in this case follicular receptivity and reactivity to the androgens delivered to the papilla/matrix unit. The pathophysiology of common baldness is strictly a misnomer as used in clinical practice since only rarely does it signify endocrine disease or other than normal physiological loss. In many patients the problem posed is essentially psychological and this aspect may be so predominant as to cause psychiatric disease.