Male pattern baldness affects around 40% of men
Genes that may increase by seven-fold the risk of early baldness amongst men have been uncovered by a team of international researchers.
Analysis of DNA from 5,000 volunteers with and without male-pattern baldness found two stretches of the genome linked with the condition.
One in seven men have both genetic variants, Nature Genetics reported.
Being able to predict hair loss early could boost development of preventive treatments, the researchers said.
An initial study in more than 500 men with early onset hair loss and 500 men without the condition highlighted the two genetic regions which substantially increased the risk of baldness.
One was the androgen receptor gene and has already been linked to male-pattern baldness.
The other region is on chromosome 20 and is nowhere near any known gene.
Male pattern baldness, or androgenic alopecia, was already k nown to be hereditary and partly caused by male sex hormones.
More work is needed to work out how this influences risk of baldness, the researchers said.
Their findings were confirmed by the researchers in other groups of people with androgenic alopecia - including women in which they found a weaker association - in the UK, Iceland and the Netherlands.
A second study also published in Nature Genetics found a similar link between hair loss and chromosome 20.
The German researchers said the androgen gene which until now had been the only gene identified with baldness was on the X chromosome which is inherited from the mother.
But chromosome 20 is inherited from both mother and father and may provide an explanation for similarities in hair loss between father and sons, they said.
Dr Tim Spector, from Kings College London, said they found around 14% of men carry both genetic variants.
"At the moment we have a fairly good diagnostic tool for people who might want to know whether they will lose their hair before they are 50.
"There probably won't be many people who want to use that at the moment because there aren't any preventive treatments."
He added he hoped it would stimulate pharmaceutical companies to develop creams, gels or pills to prevent hair loss before it starts.
"The other thing is understanding how these genes actually work - it's likely to provide use with new targets for gene therapy which is actually quite easy to deliver to the hair follicle."
Professor Val Randall, from the Centre for Skin Sciences at the University of Bradford said the work was very exciting, although it was debatable whether men would benefit from finding out about their hair loss risk.
However she added: "It is always easier to prevent than replace hair growth.
"Male pattern baldness has a strong inherited aspect and understanding that may well lead to better treatments and novel approaches."