It may be small comfort to anyone sporting a comb-over, but researchers have found a second genetic risk factor for baldness.

Two groups, working independently, found variants on chromosome 20 that are associated with male pattern baldness--the most common cause of hair loss in men, and the root of a multimillion-dollar industry devoted to protecting, nurturing, and transplanting hair.

A third report identifies a new kind of stem cell in the hair follicles of mice that, when transplanted onto the skin of hairless rodents, causes the animals to sprout tufts of hair.

These latest findings offer greater insight into the genetic underpinnings of male pattern baldness, and into the process that produces a glorious head of hair in the unafflicted. According to a research team led by Tim Spector of King's College London, figuring out the genetic variants linked to the disorder could lead to gene therapies for baldness. The discovery of a risk factor on chromosome 20 may point to "an intriguing new potential target" for gene therapy.

All three studies were published online in Nature Genetics on October 12.

Genetic tests, the researchers say, could identify people who are likely to be troubled by a receding hairline and give them the benefit of early treatment, before they're forced to smear sunblock on their naked scalps.

Despite its name, male pattern baldness, which is strongly hereditary, affects both women and men--40 percent of adults in all. There are a couple of drugs available that can slow hair loss and lead to new hair growth in some people, but the effect isn't permanent: if a patient stops the regimen, his hair will fall out. Some people opt for hair transplants, but they're time consuming and expensive.

However, this latest genetics work may have value beyond the bathroom mirror. People with male pattern baldness are more likely to suffer from cardiovascular disease, insulin resistance, and several other disorders. Scientists haven't figured out the link, but "it is quite likely that there is one genetic connection," says Axel Hillmer, formerly at the University of Bonn, in Germany, and now with the Genome Institute of Singapore, who led one of the teams that identified the risk factors on chromosome 20.

Male pattern baldness is also linked to variants in the androgen receptor gene on the X chromosome.