Scientists say a fault in how the body processes hormones could cause women to develop a condition which can cause infertility.
Polycystic ovary syndrome (PCOS) can also cause miscarriage and obesity as well as excessive hair growth and irregular periods.
Up to 10% of women in England and Wales are affected by the condition.
It is thought to be directly caused by excessive levels of the male hormone testosterone being produced.
Researchers from the University of Birmingham say in up to 5% of women this could be caused by a fault in the way the body processes the stress hormone cortisol.
Cortisol helps the body to deal with stressful situations by releasing stored energy and priming the muscles for action.
It is also important in how the body deals with infection and inflammation.
Cortisol, the active form of the hormone, can be turned into cortisone, the inactive form, by enzymes in the body.
Researchers have found some women do not have these enzymes. This means their bodies cannot process cortisol properly - which causes higher levels of testosterone to be produced.
Three women with this specific hormonal problem have been studied. The researchers are now carrying out further work looking at 150 women.
There is already a test which can detect the problem, but many women are not offered it.
If women are found to have a problem metabolising cortisol, they can be given similar hormones which perform the same role, but which the body would be able to process - preventing the dangerous build-up of testosterone.
Professor Paul Stewart of the University of Birmingham, who is leading the research, told BBC News Online: "This syndrome is a serious problem for many thousands of women.
"So even if we are helping just a small proportion of those who suffer from it we will have taken a big step forward."
But the professor, who is based at the Queen Elizabeth Hospital Wellcome Trust Clinical Research Faculty, added some words of caution.
"We really don't know, until we have done further research, how common this specific problem will be," he said.
"But when you uncover a new genetic basis for a disease, you raise awareness and more cases are discovered."
He added: "If you can understand the basis of the disease, you can target the therapy."
A spokeswoman for Verity, a support group for people with polycystic ovary syndrome, said: ""We are always very interested to see new research into the possible causes of PCOS.
"It is a complex condition affecting many thousands of women in the UK, so anything that may help to further our understanding and ultimately help women to combat their distressing symptoms can only be welcomed."
The research is published in the online version of the journal Nature Genetics.