So exactly where is hair loss inherited from? Mother's father like they tell us? An unpredictable unorganized appearance throughout family members? Dr. Richard Lee of Minoxidil.com addresses the genetics of hair loss, and gives the solid scientific answer to this age old question...
Dr. Ken Washenik, medical director of the Aderans Research Institute, has
an amusing and straightforward retort to alopecia androgenetic patients who
tell him that there is no history of MPB in their family. He simply says, “Now
there is”.
Unquestionably, the two most important factors in the etiology of the common patterned
loss of scalp hair known as male pattern baldness (MPB) are the genetic predisposition
and the dependence on androgens. Without both components, MPB does not occur.
Whereas the hormones involved in MPB (primarily testosterone and dihydrotestosterone)
have been identified, the inheritance of MPB remains only partially solved.
Is it Mom's Fault?
"Mom"
It’s an enduring and common misconception among patients that MPB is ‘inherited
from the mother’s side’. Well, that statement is neither right nor
wrong. Pattern baldness can be inherited from the mother’s side. But it
can also be inherited from the father’s side. Despite the universal interest
in the genetics of MPB, there is a surprisingly small number of scientific studies
in regards to the genetics of MPB and there is only one known extensive family
study on MPB. This study of hair growth patterns in 22 families concluded that
common pattern baldness was an autosomal dominant phenotype in men and an autosomal
recessive phenotype in women. However, the validity of these results are controversial
because of a lack of details regarding examination methods and sampling errors
of this study, which was published in 1916.
Despite the fact that the entire human genome, comprising approximately 30,000
genes in the human DNA, was completely mapped out as of April 2003, the gene
or, more likely, genes responsible for MPB, have not been identified. Studies
of the genes (on chromosome Xq11.2^q12) encoding the two 5alpha-reductase isoenzymes
show that they are not the genes associated with male pattern baldness.
What is known is that the age of onset, the rate of progression, and the pattern
of follicular miniaturization are all influenced by heredity. Generally, the
earlier the onset of balding, the more extensive the degree of hair loss will
eventually be.
There are often times when an accelerated rate of progression of MPB will coincide
with some other event, such as a change in medication, or the onset of another
medical disorder, or a change in habits, etc. Although these events may cause
hair loss, they do not precipitate or aggravate MPB.
Maybe we can blame Dad?
A study examining 410 men with premature baldness found evidence of a genetic
influence from the father’s side in only 236 cases. Hair loss similarities
between father and son have also been observed in another study in regards to
the frequency of MPB in brothers of men having prematurely bald fathers (66%)
compared with brothers of men with unaffected fathers (46%). The relatively strong
association of MPB between fathers and sons in this study was not consistent with
a simple Mendelian autosomal or sex-linked dominant inheritance and suggested
that several genes (a polygenic etiology) may be responsible for MPB. As further
evidence against a single and/or X-linked gene being responsible for MPB is the
observation that only 33% of the fathers of 18 women suffering from severe pattern
baldness also had MPB. These findings suggest that other autosomal genes play
an important role in the expression of MPB.
Dr.
Richard Lee
Dr. Lee obtained his degree in medicine from the University
of Pittsburgh, and has founded and operated one of the few private medical
practices devoted entirely to the research and treatment of hair loss..
"Regrowth" was incorporated in 1987. Dr.
Lee provides consultation services to hair loss sufferers, and has a line
of custom minoxidil and topical spironolactone solutions which are widely
used by our members here at HairlossTalk.com. Dr. Lee is a respected member
of the HairlossTalk Community, and one of the few physicians truly educated
on the causes and treatments of hair loss. You can see his website and products
at http://www.minoxidil.com
Considering the high proportion of men affected by MPB, its distribution in the
general population, the increased risk of MPB as the number of affected close
relatives increases, and the high risk of inheritance from either or both affected
parents, one can support a strong argument in favor of a polygenic inheritance.
It seems ironic that with all the knowledge that has been accumulated in regards
to MPB in the past several decades, we still do not know the exact genetic inheritance
of MPB. What is known is that the genes are autosomal (not on the X or Y chromosomes),
dominant (as opposed to recessive), and have variable penetrance (so it may
not affect siblings of the same parents to the same degree).
References:
Ellis JA, Stebbing M, Harrap SB: Genetic analysis of male pattern baldness and
the 5alpha-reductase genes. J Invest Dermatol. 110(6):849-53, 1998
Harris H: The inheritance of premature baldness in men. Ann Eugenics 13:172-181,
1946
Neale MC, Cardon LR: Methodology for Genetic Studies in Twins and Families. NATO
ASI Series. Dordrecht: Kluwer Academic Publishers, 1992
Kuster W, Happle R: The inheritance of common baldness: Two B or not two B?
J Am Acad Dermatol 11:921-926, 1984 Salamon T: Genetic factors in male pattern
alopecia. In Baccaredda-Boy A, Moretti G, Frey JR (eds): Biopathology of Pattern
Alopecia. New York, Karger, pp 39-49, 1968
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