Because human hair plays important roles in social and sexual communication (discussed in Section 1.2), hair where it is unwanted or hair loss is a source of embarrassment and psychological distress. A variety of methods are available to help control both excess hair growth and hair loss. The earliest methods used to remove hair were physical means such as shaving, followed by depilatory creams, waxes, or sugars; new developments include the use of lasers (see Chapter 10), and chemical inhibitors of hair growth such as Vaniqua [216,215]. Many substances have been suggested to stimulate hair growth over the years [20,217] with one of the most recent also being laser treatment. However, the most established promoters are topical applications of minoxidil (Regaine) or oral finasteride (Prope – cia) a 5a-reductase inhibitor used to block androgen effects in androgenetic alopecia [161]. The mechanism of action of minoxidil, an antihypertensive agent that promoted hair growth as an unacceptable side effect, has been a mystery despite its use for over 20 years; recent research supports action via potassium channels in the dermal papilla [218,219]. The most effective method remains transplanting androgen-independent hair follicles from the base of the scalp to the affected areas where they retain their intrinsic independence to androgens and maintain terminal hair [156]. Current research includes attempts to culture cells from hair follicles to amplify the individual’s donor follicles.
Despite this range of treatments, neither excess hair growth nor hair loss are fully controlled; since much unwanted hair growth or hair loss is potentiated by androgens, any treatment has to be applied frequently and continually to counteract the constant supply of hormonal stimulation. Recently, successful clinical response to finasteride was related to increased dermal papilla expression of IGF-1 [220], confirming the importance of dermal papilla-produced paracrine factors and emphasising the dermal papilla’s key role in androgen action. Greater understanding should lead to exciting new ways to treat hair disorders, as molecular pharmacology can devise very specific drugs and transport through the skin can target particular areas.