[Androgenetic alopecia. Current aspects of a common phenotype]

Androgenetic alopecia is the most common type of hair loss in men and women. The disorder represents a quantitative phenotype with an underlying genetic disposition. So far none of the causative genes have been identified. Under the influence of androgens there is a shortening of the anagen phase as well as a reduction of the cellular hair matrix volume in the involved scalp area. This results in the transformation of thick terminal hair follicles into thin vellus-like hair follicles. Clinically, patients present with an alopecia that follows a defined pattern (pattern baldness) and progresses continuously but in varying degrees. In advanced cases, men may develop baldness with remaining hair exclusively in the temporal and occipital regions. Women are prone to exhibit a more diffuse type of hair loss with pronounced thinning in the parietal region. Whereas the diagnosis of androgenetic alopecia is easy, its treatment is often difficult. The physician is commonly confronted with high patients' expectations regarding hair regrowth. Today, with minoxidil and finasteride, effective therapies are available which can lead to cessation of hair loss. The identification of underlying genes will make a more specific therapy easier to achieve.