Hair Loss General Information

Normally, individuals will lose on average between 40-100 hairs per day of the 100,000 hairs present on the scalp.  During any given time, 85-90 percent of an individual's hair is in the growing phase advancing in length by ½ -1 inch per month.  Hair can continue to grow from 2-6 years, when the growth phase ends the hair follicle starts a 2-6 month phase of resting and then shedding.  Usually, only 10-15 percent of an individual's hair is in the resting or shedding phase at any given time.  Randomly, new hair follicles begin to replace the shedding follicles producing a healthy cycle. However, in cases of androgenetic allopecia this natural cycle is disrupted.

Ninety-five percent of hair loss is attributable to androgenetic alopecia, more commonly known as hereditary hair loss or in men male pattern baldness.  In men, the condition frequently progresses to the horseshoe fringe of hair.  While in women it manifests itself as a generalized thinning of the hair over the entire scalp.  Several hypothesis for this condition exist, however, most research of late has focused on a genetic predisposition and the presence of dihydrotestosterone (DHT).  Every hair has a genetic predisposition, the gene that determines whether an individual will be susceptible to androgenetic alopecia is located on non-sex chromosomes that determine the genetic makeup of all cells.  Contrary to the popular myths concerning these genes they can be inherited from either parent's relatives.  Researchers believe that DNA is somehow responsible for the increased sensitivity of hair follicles to the hormone DHT.  This hormone results from the breakdown of testosterone by an enzyme called alpha-5 reductase. 

DHT causes the hair follicle to atrophy, reducing in size until only vellus hair is produced.  Vellus hairs are short fine non-pigmented hairs which are difficult to see.  As the diameter of the hair shaft continues to decrease in size the sebaceous glands continue to secrete the same volume of sebum (fats and oils which lubricate the hair).  This results in an oily scalp and subsequently flatter hair. The process continues until the vellus hair is no longer produced and individuals develop the characteristic hair loss pattern.