Researchers in Germany have found that variations in a gene related to male sex hormones may be at the root of male-pattern baldness, the most common form of hair loss. The culprit is the androgen receptor gene, and it dwells on the X chromosome, which all men inherit from their mothers.

Experts have long believed that hair loss in inherited. But the new research, to be published in the American Journal of Human Genetics, is the first to identify a specific gene that may be involved, according to the study authors.

Other, yet-unidentified genes are likely involved in male-pattern baldness, possibly including ones handed down by fathers. But the new findings highlight the importance of mom’s side of the family when it comes to a man’s hairline, according to the study authors, led by Dr. Markus M. Nothen of the University of Bonn.

A young man concerned about the future of his hair may do better to look toward his maternal grandfather’s hair history rather than his father’s, according to the researchers.

Their study included 95 German families in which at least two brothers had begun losing their hair before the age of 40. Using blood samples from these men and other family members without early hair loss, the researchers found that a particular variant in the androgen receptor gene occurred much more frequently among men with early male-pattern baldness compared with men who retained a full head of hair past the age of 60.

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The androgen receptor gene helps govern the workings of male sex hormones (androgens), such as testosterone. Though these hormones promote the growth of body and facial hair, on the scalp excess androgens may cause hair loss.

It’s possible, according to Nothen and his colleagues, that the suspect gene variant creates a greater number of androgen receptors in the scalp - and therefore stronger androgen activity.

The researchers say they are continuing to hunt down the other genes involved in early-onset male-pattern baldness. Scientists hope that getting at the genetic roots of hair loss will eventually spawn better baldness treatments or a cure.

SOURCE: American Journal of Human Genetics, July 2005.