Dihydrotestosterone
Dihydrotestosterone is an endogenous androgen hormone that is known to cause hair follicles to minimize which causes hair loss in both men and women.
Male pattern hair los is the most common type of hair loss in men and can also affect women. Hair at the temples and on the crown slowly thin and eventually disappear. The exact reason why this happens is unknown, but genetic, hormonal, and environmental factors is all thought to play a role. DHT is believed to be a major factor.
3 (4) Phases of Hair Growth
Hair Growth is split into 3 phases: Anagen, Catagen, Telogen and Exogen
- Anagen- The growth phase. Hairs remain in this phase for 2 to 6 years. The longer it lasts, the longer the hair grows. Normally 80-85 percent of the hairs on the head are in this phase.
- Catagen- The regression phase. Lasts only 2 weeks. It allows the hair follicle to renew itself.
- Telogen- The resting phase. The follicle lies dormant for 1 to 4 months. Normally between 12 and 20 percent of hairs are in this phase
- Exogen- The anagen phase begins again. The existing hair is pushed out of the pores by new growth and naturally sheds.
Hair Loss:
Hair loss happens when the follicles slowly become minimized, the anagen phase is reduced, and the telogen phase becomes longer. The shortened growth phase means the hair cannot grow as long as before. Over time, the anagen phase becomes so short the new hairs cannot peek through the surface of the skin. Telogen hair growth is less well-anchored to the scalp making it easier to fall out.
As the follicles become smaller, the shaft of the hair becomes thinner with each cycle of growth. Eventually, the hairs are reduced to vellus hairs, the type of hair found on an infant.