Osteoporosis literally means that the bones become porous, and break
People with coeliac disease may be more susceptible to osteoporosis because their own immune system attacks their bone tissue, a study suggests.
Osteoporosis is a known risk of coeliac disease and has been explained by a failure to absorb calcium or vitamin D.
But a study in the New England Journal of Medicine suggests coeliac patients produce antibodies which attack a key protein that maintains bone health.
They could easily be treated with drugs to prevent bone loss, researchers say.
It also explains why osteoporosis in those with the digestive disorder may not respond to calcium and vitamin D.
Coeliac disease is caused by a reaction to gluten, a protein found in wheat, barley, rye and oats which damage the small finger-like villi that line the small intestine and play a key role in digestion.
When damaged and inflamed, the villi are unable to absorb food properly, causing diarrhoea and malnutrition.
It affects one in 100 people, and of these a significant proportion may go on to develop osteoporosis - a disease of bone that leads to an increased risk of painful and disabling fractures.
Scientists at the University of Edinburgh say it may be a protein called osteoprotegerin which holds the key to the link between coeliac disease and osteoporosis.
In 20% of the coeliac patients tested, antibodies were produced which stopped this protein - crucial for maintaining bone strength - from working effectively.
Lead researcher Professor Stuart Ralston from the Institute of Genetics and Molecular Medicine, said: "This is a very exciting step forward. Not only have we discovered a new reason to explain why osteoporosis occurs in coeliac disease, but we have also found that it responds very well to drugs that prevent bone tissue removal.
"Testing for these antibodies could make a real and important difference to the lives of people with coeliac disease by alerting us to the risk of osteoporosis and helping us find the correct treatment for them."
Sarah Sleet, head of Coeliac UK said: "Osteoporosis is a damaging complication of coeliac disease and our traditional understanding of its cause has left some people with the condition with little hope that their symptoms and quality of life will improve.
"This new breakthrough in understanding and treatment will give renewed hope to our members struggling with their condition."
Dr Claire Bowring, medical policy officer with the National Osteoporosis Society said: "We already know that coeliac disease is a risk factor for osteoporosis and that early diagnosis and treatment of coeliac disease gives the best chance of improving bone density.
"A better understanding of the relationship between coeliac disease and osteoporosis will enable clinicians to manage both conditions more effectively.
"Although this research is at an early stage it is certainly interesting and we look forward to more extensive work to identify how prevalent this antibody is in people with coeliac disease."