Prostanoids and Hair Follicles: Implications for Therapy of Hair Disorders.

Prostanoids, including prostaglandins (PGs) and thromboxane A2 (TXA2), are a family of lipid-derived autacoids that modulate many physiological systems and pathological contexts. Prostanoids are generated by sequential metabolism of arachidonic acid, catalysed by cyclo-oxygenase, to PGH2, which is then converted to PGD2, PGE2, PGF2α, PGI2 and TXA2, catalysed by their specific synthases. Recent evidence suggests that prostanoids play a role in regulating hair growth. The PGF2α analogue is Food and Drug Administration-approved in the US and routinely used to enhance the growth of human eyelashes. PGE2 is reported to protect from radiation-induced hair loss in mice. Conversely, PGD2 inhibits hair growth. This paper reviews the metabolism of prostanoids and the expression pattern of prostanoid receptors in hair follicles, focussing on their different and opposing effects on hair growth and the underlying mechanisms. This has potential clinical relevance in the treatment and prevention of hair disorders.