It is important to understand the
normal hair growth cycle to understand why hair loss occurs. The hair follicle
is an anatomical structure that evolved to produce and (push out) a hair
Normal Hair Growth
All folicles repeatedly cycle
through the following 3 stages.
||1. Anagen Stage (growth)
The new hair grows from the
base of the follicle. This growth phase usually lasts for a number
of years and results in a full-grown hair.
||2. Catagen Stage (resting)
During this stage the hair
stops growing and the hair root shrinks. The base of the follicle
breaks dow and the hair moves upward in the follicle, away from the
root and the blood vessel supplying it with nutrients.
||3. Telogen Stage (re-growth)
The mature hair is now only
loosely anchored to the hair root. It usually falls out after a few
months or is pushed out by the next hair growing up below it.
The Hair Loss Process
||How DHT Affects Normal Hair Growth
The hair roots receive nutrients
from blood vessels which contain blood cells (red) and a hormone called
testosterone (blue). Testosterone is converted to another hormone
called DHT (yellow) by the actions of an enzyme called 5 alpha reductase.
DHT Shortens the Hair Growth Phase
When DHT is present in the scalps of men genetically predisposed
to male pattern hair loss, the following happens:- the anagen growth
phase is shortened so the hair is shorter when it stops growing. -
over time the follice produces hair that gets progressively shorter
and less pigmented.