Diabetes drugs may thin women's bones

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Diabetes drugs may thin women's bones

Study finds that the risk of fractures could be increased for women, but not for men

A group of drugs used to treat type 2 diabetes could cause bone thinning in women and significantly increase their risk of fractures, say UK and US researchers reporting in the Canadian Medical Association Journal

The team analysed the results of 10 previous studies that looked at the risk of fracture for patients taking a group of drugs known as thiazolidinediones. All 10 had lasted at least 12 months and when pooled together involved more than 13,000 people – the largest analysis of its kind. They found that thiazolidinediones were associated with a 45 per cent increase in fractures, but only in women. No similar increase was seen in the men studied.

Thiazolidinediones are a group of drugs used to control blood sugar levels in people with type 2 diabetes, a form of the disease that is most commonly found in the over 50s. Included in this group are the drugs rosiglitazone (Avandia) and pioglitazone (Actos). Thiazolidinediones have previously been found to raise the risk of heart failure. However, the drugs are considered effective treatments for type 2 diabetes. Last year, there were around two million prescriptions for rosiglitazone and pioglitazone.

The researchers also found that these two drugs were associated with significant bone loss, particularly in the hip and lower spine. The authors estimate that one in 55 women at low risk of fracture who take a thiazolidinedione for one year would suffer a fracture. However, among older women at higher risk the figure may be as many as one in 21 women.

"In one of the large trials we looked at, women taking other diabetes medication had about a 1.5 per cent fracture risk per year, but this went up to just under three per cent with the thiazolidinediones," said Dr Yoon K Loke, Senior Lecturer in Clinical Pharmacology at the University of East Anglia and one of the team's researchers.

More research is needed to understand why the bone thinning occurs, but one theory is that the drugs weaken the strong calcium structure of the bones, possibly replacing it with fat cells.

The report urged clinicians to limit prescriptions of the drugs to older women who are at higher risk. However, Dr Loke stressed that women shouldn't suddenly stop their treatment: "This is a problem that arises with long-term use, and patients should not stop or change their treatment suddenly without consulting their doctor."

The report is a review of previous research and so the findings won't come as news to many doctors, already aware of the risks. In fact GlaxoSmithKline, the drugs company that makes Avandia, carried out its own research into the link last year and include a warning of the increased risk of fracture in the drug's information leaflet.

NICE, the UK body that sets guidelines of use for medications, recently updated its prescription guidelines for thiazolidinedione stating that doctors should not prescribe thiazolidinediones to those at higher risk of fracture.

"Both the Medicines and Healthcare Products Regulatory Agency and the European Medicines Agency say that people should certainly not stop taking thiazolidinediones and if concerned they should consult their doctor," says Dr Victoria King, research manager for the charity Diabetes UK.

The European Medicines Agency carried out a safety review of rosiglitazone and pioglitzone last year, and concluded that their benefits in managing type 2 diabetes outweighed their risks.

"I think that women should try to avoid taking these drugs for more than a year," advises Dr Loke. "They should speak to their doctors about other treatment options, given that there are many other choices available nowadays."

Dr Loke is now considering further research. "It would be good to find out if we can give any treatment such as calcium, vitamin D, or other bone-strengthening drugs to reverse this loss of bone density in women who have been on these diabetes drugs."

Website: Diabetes UK: www.diabetes.org.uk

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