Facts About Hair

Hair is an essential element of our image and overall aesthetics. In addition to improving our appearance hair also has a protective element.  It helps shield our scalp from damage, slows down heat loss in the winter, and protects us from solar radiation in the summer.

The human body has about five million hair follicles, of which 100,000 to 150,000 reside on the scalp.  Also, hair color can determine the total number of follicles one’s head has.  Blonds have the most, brunettes have fewer than blonds, and redheads have the least amount of hair follicles.

The Cycle of Hair Growth

Hair grows about ¼ to ½ inch in one month’s time and has a cyclic pattern that is influenced by factors as genetics, medications, disease, or other conditions that can lead to hair loss.

It is within the follicles where hair is formed.  Hair then takes on an ongoing cycle of growth and rest as it expands out of the follicle.  The hair growth cycle can be split into three phases:

  • Anagen – the 2 to 8-year growth phase where there is active hair growth;
  • Catagen – a 2 to 4-week degeneration phase as the follicle is nearly fully depleted; and,
  • Telogen – a 2 to 4-month resting phase that occurs before recreating another anagen phase and a new hair shaft.

To be created, a new hair shaft must first push out the former or “dead” hair shaft causing shedding.  For those who find hair in our brushes, combs, or in the shower drain, we are losing about 50 to 100 telogen hairs a day.  As for a healthy scalp that is free of any condition leading to hair loss, its telogen phase is about 10% of the total follicles in a specific time period.

The Hormone Role in Hair Loss

Hormones are a vital factor influencing hair growth in men and women who experience pattern hair loss.  Androgens are hormones that play an essential role in hair growth and in inherited male and female hair loss patterns.  Hence, the main controlling androgens are testosterone, its metabolite, and dihydrotestosterone (DHT):

  • Testosterone enables growth in pubic, underarm, and beard hair.
  • Dihydrotestosterone is associated with scalp hair loss and hair growth that is not under androgen control.  DHT combined with the presence and activity of hair loss genes(s) are major elements attributing to pattern hair loss in men and women.

The Genetic Role in Hair Loss

Hair loss pattern attained by either gender is coined as androgenetic alopecia (AGA) since both androgens (andro) and genes (genetic) attribute to it.  Hence, hair loss has a medical term: alopecia.

AGA is basically a genetic condition that “runs in families”.  DHT and the gene for hair loss are both needed to cause AGA.  The hair loss gene causes scalp hair follicles to be extremely sensitive to DHT causing them to (1) stop producing hair, or (2) make only “peach fuzz” (miniaturized) hair.  The level of DHT need not be extra high for AGA to form.  AGA is formed by the presence of the gene that enables DHT to stop hair follicle growth.

It is often impossible to predict the inherited patterns of hair loss for just anyone.  Just because an uncle or a father lost hair because of AGA, a son or daughter can’t be assumed to have that same pattern.  For an analysis of AGA genetics, one is recommended to see a physician hair restoration specialist.  They are educated in the onset and progression of pattern hair loss in men or women and can counsel one accordingly.