May 27, 2005 -- Mothers may unwittingly put their sons on the path to baldness. Chalk it up to genetics, says European researchers.
They include Markus Nöthen, a genomics professor at Germany's University of Bonn. Nöthen and colleagues say they've found a gene variation that may explain some cases of male pattern baldness (androgenetic alopecia), the most common form of hair loss, which is related to the male sex hormones.
The suspect gene variation sits on the X chromosome, which is handed down to men by their mother. So a man may get an idea of his scalp's future from men on his mother's side of the family.
A white man's chance of male pattern baldness increases with age; in his 50s, he has a 50% chance of having at least some hair loss, the study shows.
Clues From Granddad
"The fact that family studies of [male pattern baldness] have typically stressed the resemblance of fathers and sons is understandable, given the differences in patterns of hair loss between males and females," write Nöthen and colleagues.
"Our genetic data, however, stress the relative importance of the maternal line in the inheritance of [male pattern baldness]. This suggests that ... the resemblance should be greater between affected males and their maternal grandfathers than between affected males and their fathers."
About the Gene
Nöthen's team studied 95 families in which at least two brothers had premature male pattern hair loss. The group included about 200 affected men.
Genetic screening showed that the "cardinal prerequisite" for premature male pattern baldness was a variation in the androgen receptor gene. The gene variant was found "very much more often" among prematurely bald men than among men who still had a full head of hair after age 60, says Nöthen in a news release.
Androgens are male sex hormones, such as testosterone. Nöthen's colleague, Alex Hillmer, says the exact mechanisms aren't known, but the gene variation seems to boost androgens' effects, leading to hair loss.
Male hormones are responsible for excess body hair, except for on the scalp where excess male sex hormones can lead to baldness.
Not the Sole Cause of Baldness
Baldness may also be influenced by other genes, some of which could come from fathers, the study notes.
"We have indications that other genes are involved, which are independent of the parents' sex," says Nöthen. So hair loss could be a father-son inheritance, too.