Common Causes of Hair Loss

A number of diseases and conditions cause hair loss, but most
people go bald because of the influence of genetics, hormones,
and time. Stress may cause additional loss, more so in women than
in men.
Looking at Grandpa’s head
In the genetic hair loss lottery, Grandpa’s important, but doctors
actually look a few generations back on the entire family tree —
men and women — in order to determine if you’ve inherited a
genetic type of pattern baldness.
Everyone inherits genetic tendencies from their parents. As you
may or may not recall from biology class, pairs of DNA segments
called chromosomes carry the information that contains the poten-
tial for different characteristics. A gene is a single bit of chemically
encoded hereditary instruction located on a chromosome.
The genetics of androgenetic alopecia (ANA), also called androge-
netic alopecia or male pattern baldness, is complicated. At least
four genes are responsible for hair loss. When several genes need
to be present for a trait such as hair loss, the trait is said to be
polygenic. Genes that are located on the X or Y chromosomes are
called sex-linked, and genes on the other 22 pairs of chromosomes
are called autosomal.
Currently, doctors believe that the genes governing common bald-
ness are autosomal (not tied to the sex chromosome) and there-
fore can be inherited from the mother’s or the father’s side of the
family. The commonly held notion that baldness comes only from
the mother’s side of the family is false, although for reasons not
fully understood, the predisposition inherited from an affected
mother is of slightly greater importance than that inherited from
an affected father. Doctors also believe that the genes involved in
androgenetic alopecia are dominant, meaning that only one gene of
a pair is needed for the trait to show up in the individual. So even if
only one of your parents passed on the baldness gene, you’re likely
to have some hair loss.
The inherited gene isn’t always ‘expressed,’ so it’s possible to
carry the gene for balding and never become bald. It can skip a
generation or two, so only looking at the generation before you
doesn’t tell you what may happen on your head.
The ability of a gene to affect you is called expressivity.Expressivity
occurs depending on a number of factors, the major ones being
hormones and age, although stress and other factors may also play
a role. Put simply, a man whose father and uncles are severely bald
may have minimal hair loss because the expression of the baldness
gene is limited. If you are confused by this explanation, imagine the
experts who try to clarify the unexplainable by putting together
the many variables and not coming up with a logical, scientific
process.
The end goal of gene identification is to manipulate genes to pre-
vent or reverse common baldness. But doctors first need to find
and fully understand which genes cause the balding process and
why are these genes expressed one way in you and another way in
your brother.