The hope is the finding could one day lead to a screening test
SUNDAY, Oct. 12 (HealthDay News) -- New genetic links to male pattern baldness have been discovered by researchers in England and Germany.
It's the second genetic connection to the kind of hair loss that many men -- and women -- experience as they grow older, said Felix F. Brockschmidt, a postdoctoral fellow at the University of Bonn and one of the authors of a report published online Oct. 12 in the journal Nature Genetics.
"The first gene known until now is on the X chromosome," Brockschmidt said. "It is the most important for alopecia [hair loss]. We are sure that this new locus we found is the second most important."
The discovery could open the way for genetic tests to single out men most likely to lose hair as they age, Brockschmidt said. "Screening for the X chromosome locus and also for this new one can possibly show the risk of male pattern baldness," he said.
But whether something can be done to prevent hair loss in people with the gene variants is another story, Brockschmidt acknowledged. One of the new studies was financed, in part, by Glaxo SmithKline, a pharmaceutical company that might seek commercial benefit from its support. And one small company already markets a $149 genetic screening test for male pattern baldness.
That test looks at variants of a gene governing receptors for androgens, which are male hormones. That gene location, on the X chromosome, was identified only a few years ago. A man has only one copy of the X chromosome, inherited from his mother. The new gene locus is on chromosome 20. Men and women alike have two copies of chromosome 20, inherited from both father and mother.
Any preventive treatment is far in the future, Brockschmidt stressed. "As soon as we know the gene and how it functions, we can do something," he said. "Right now, we have identified the locus but not the gene."
The work done in Germany paralleled a study led by researchers at Kings College London, with the results of that study differing slightly. It included 1,125 men assessed for male pattern baldness. Two regions on chromosome 20 were found to be associated with the condition. And a further study of another 1,650 men found a sevenfold increase in the incidence of baldness in the one in seven men carrying variants in both the X chromosome and chromosome 20 regions.
The new results "are certainly putting us closer to a genetic test for developing alopecia," said Dr. George Cotsarelis, director of the Hair and Scalp Clinic at the Hospital of the University of Pennsylvania.
But, he added, a negative reading on such a test would be more informative than a positive result showing the presence of the baldness-related genes.
"If you don't have the genes, there is a negative predictive value of 96 percent," he said. "If you do have the genes, there is a positive predictive value of about 14 percent."
The currently marketed genetic test got a low grade from Cotsarelis. "It can predict baldness 60 percent of the time, and 50 percent of men will become bald," he said.
Learn more about what's known about male pattern baldness at the U.S. National Library of Medicine.
SOURCES: Felix F. Brockschmidt, Ph.D., postdoctoral fellow, University of Bonn, Germany; George Cotsarelis, M.D., director, Hair and Scalp Clinic, Hospital of the University of Pennsylvania, Philadelphia; Oct. 12, 2008, Nature Genetics, online
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