Male pattern baldness is an inherited condition and the gene can
   be inherited from either the mother or father’s side. There is a
   common myth that inheritance is only from the mother’s side.

  This is not true.   

   It is estimated that 35 million men in the United States 
   are affected by male pattern baldness or androgenetic alopecia.
 
  "Andro" refers to the androgens (testosterone, dihydrotestosterone)
   necessary to produce male-pattern baldness (MPB).

  "Genetic" refers to the inherited gene necessary for MPB to occur.
   In men who develop male pattern baldness the hair loss may begin
   any time after puberty.

In some men, initial male-pattern baldness may be delayed until the late 30’s or 40’s. It is generally recognized that men
in their 20’s have a 20 percent incidence of male pattern baldness, in their 30’s a 30 percent incidence of male pattern
baldness, in their 40’s a 40 percent incidence of male pattern baldness, etc. Using these numbers one can see that a
male in his 90’s has a 90 percent chance of having some degree of male pattern baldness.

The hair growth cycle is affected in that the percentage of hairs in the growth phase (anagen) and the duration of the
growth phase diminish resulting in shorter hairs. More hairs are in the resting state (telogen) and these hairs are much
more subject to loss with the daily trauma of combing and washing. The hair shafts in male pattern baldness become
progressively smaller in diameter and length, with time. In men with male pattern baldness all the hairs in an affected
area may eventually (but not necessarily) become involved in the process and may with time cover the region with fine hair.