Scientists have identified a gene which they believe may play a key a role in determining who develops osteoporosis or brittle bone disease.
Osteoporosis affects more women than men
The gene called Alox15 affects the density of important minerals in bones.
Lifestyle factors, such as poor diet, can increase the risks of developing osteoporosis. However, scientists have also suspected genes are involved.
This finding, published in the journal Science, could lead to new drugs to fight the condition.
Dr Richard Klein and colleagues at Oregon Health & Science University based their findings on tests on mice.
They bred genetically engineered mice which lacked the Alox15 gene.
They found that these mice had greater bone mineral density and a much lower risk of developing osteoporosis.
Further tests showed that blocking chemicals produced by this gene also boosted the mineral density of bones.
"Animals that had over-expression of the gene had the lowest bone density," said Dr Klein.
"Knockout mice, which do not have the gene, have very high bone mass."
While further research is needed, the scientists believe the gene has a similar effect in humans.
The findings raise the prospect of drugs to stop this gene from producing the chemicals that may weaken bones.
Osteoporosis affects one in three women and one in 12 men. It is responsible for 200,000 breaks every year in the UK and around 40 deaths a day.
It is often known as a silent illness, because many people do not know they have it until it is too late.
A diet high in calcium and regular exercise can protect against the disease.