Why do some men go bald, while others are full-thatched well into old age? Until now, the blame—er, answer—was believed to rest with mom. That's because it is the mother's X-chromosome that carries the known gene for male pattern baldness. Fathers were blameless. Well, not anymore. Studies published this week in the journal Nature Genetics indicate that two genetic variants on an entirely different chromosome are associated with male pattern baldness. In fact, these variants will raise your risk of going bald sevenfold.
For many years, researchers have been aware that a particular genetic variant on the X-chromosome is associated with male pattern baldness—and at least three-quarters of male baldness is believed to have genetic causes. Of course, men only have one X-chromosome, which they get from their mothers. Their other sex chromosome is a Y-chromosome, received from their fathers. The gene variant for baldness is believed to be recessive, so in women, who have two X-chromosomes (one from their father and one from their mother), the baldness is very rarely expressed. Men, however, have no second X-chromosome. If they get the baldness variation from their mother's X-chromosome, that recessive quality will come out in full force. Presto! Baldness. "That's where the idea that baldness is inherited from the mother's side of the family comes from," explained study author Dr. Brent Richards of McGill University and Jewish General Hospital. "However, it's been long recognized that that there must be several genes causing male pattern baldness. Until now, no one could identify those other genes."
This more complex notion of the sources of baldness makes good genetic sense. After all, the X/Y sex chromosomes are only the final of 23 pairs of chromosomes each person receives from his or her parents—one chromosome in each pair from each parent. So, the researchers from McGill University, King's College London and GlaxoSmithKline Inc. began investigating other possible genetic culprits on other chromosomes. Along with European colleagues—in the Netherlands and Switzerland—they studied the genetics of 1,125 caucasian men who had been assessed for male pattern baldness. Their research was persuasive enough that they followed up with 1,650 more men. A similar study was conducted by Australian and German researchers on nearly 650 men. Both studies found variations on the twentieth chromosome that were closely associated with male pattern baldness. And the McGill/King's College study isolated two particular variants with a pretty potent effect. The results were, as Dr. Richards describes them, "startling". He says, "If you have both the risk variants we discovered on chromosome 20 and the unrelated known variant on the X chromosome, your risk of becoming bald increases sevenfold. What's startling is that one in seven men have both of those risk variants. That's 14 per cent of the total population!" In other words, a substantial proportion of baldness is influenced by genetic variants not on the X-chromosome, and therefore inheritable from either parent. You really owe your mother an apology for blaming her.
What is the benefit of this research? As Dr. Richards points out, "We've only identified a cause. Treating male pattern baldness will require more research. But, of course, the first step in finding a way to treat most conditions it is to first identify the cause." And, as his colleague Dr. Tim Spector of King's College points out, "Early prediction before hair loss starts may lead to some interesting therapies that are more effective than treating late stage hair loss." This would be a huge injection into the baldness industry. Baldness affects roughly half of men by the time they're fifty years old; by the time they're in their eighties, the number is closer to 75 percent. The money flowing in and out of the baldness industry in the U.S.—treatments, procedures, cover-ups—is often estimated to add up to a billion dollars per year. New and more effective treatments based on genetic information could offer hope to millions of men afflicted with this condition. But it will take time—so don't stop the Rogaine just yet.