...Studies demonstrate that loss of hair follicles involves distinct patterns of expression of active caspases. Active caspase 8, an initiator of the death receptor pathway, was predominately found in the isthmic and upper lower portion of the shaft. This pattern of expression suggests that the death receptor pathway is activated during hair regrowth and is initiated by toxic substances that bind to death receptors, i.e., TNF-alpha. Interestingly, activated caspase 3, a downstream effector caspase, was higher in catagen hair then in other phases of the hair cycle, indicating a role in the terminal stage of the apoptotic pathway. Activated caspase 1 was also found in the hair bulb and hair shaft. This study suggests an important role of the infundibular area of the hair shaft where inner and outer root sheath are abruptly changing and that this area may play a role in the regulation of normal hair apoptosis. Caspase 3 seems to be playing the key role in the apoptotic pathway during the catagen phase of the hair cycle in these areas. Finasteride may exhibit its influence by selectively inhibiting DHT, which affects a multitude of "androgen responsive genes", such as the caspase pathway, which affects programmed cell death in the hair regrwothcycle