One man in seven has a genetic profile that will raise dramatically his chances of going bald at a young age, according to research that could lead to new ways of predicting and preventing hair loss.

Men who inherit two particular genetic variants are seven times more likely to develop male pattern baldness by their forties than those who carry neither, a British-led team has found.

The discovery, from the first study to trawl the human genome for passages of DNA linked to baldness, will allow young men to discover with much greater accuracy whether and when they are likely to lose their hair.

Some may then wish to try drugs such as finasteride (marketed as Propecia), which can delay, stop or even reverse baldness, while they still possess luxuriant locks.

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The research should also assist the development of new treatments. Professor Tim Spector, of King’s College London, who led the study, said: “Early prediction before hair loss starts may lead to some interesting therapies that are more effective than treating late-stage hair loss. It will encourage pharmaceutical companies to produce preventive lotions that might stimulate hair follicles before it’s too late.”

Brent Richards, of McGill University in Montreal, Canada, who contributed to the research, said: “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 is to identify the cause.”

Tests for the genes are soon to be offered by deCODE Genetics, an Icelandic company that took part in the study, through its deCODEme personal genotyping service.

The findings, which are published in the journal Nature Genetics, also add to understanding of how baldness runs in families.

One of the two DNA regions that is implicated controls a male hormone receptor and is carried on the X chromosome, of which men have just one copy that is always inherited from their mothers. This variant, which was already known, may account for the common observation that men often take after their maternal grandfathers in trichological matters.

The second DNA region, which has been newly identified, is on chromosome 20, of which men have two copies, one inherited from each parent. This means that at least some of men’s susceptibility to hair loss is passed on by their fathers.

About a third of men are affected by male pattern baldness by the age of 45, and two thirds by the age of 60. It also affects women, though more rarely, and tends to lead to generalised hair thinning rather than the characteristic pattern of loss seen in men. The new research suggests that men with the two genetic variants have a 70 per cent or greater chance of going bald early, while those who carry neither have a chance of about 10 per cent. About 14 per cent of men have the two variants.

Researchers used a new gene-hunting technique, genome-wide association, to search for variants that might be linked to baldness in a sample of 1,125 white European men from Switzerland.