It has been well understood that women with type 2 diabetes who take Avandia or Actos to control the disease are at a higher risk of bone fractures than diabetic men taking the same medications. Until today’s release of a study report conducted at Wake Forest University School of Medicine, the extent of the increased fracture risk has been unknown. After reviewing data from 10 clinical studies involving 14,000 diabetic patients, the research team says the fracture risk to diabetic women is twice that of men.

This finding comes as a bit of a double whammy for diabetic women, since women become more prone to fractures than men as they age, whether or not they are diabetic.

Avandia (rosiglitazone), made by GlaxoSmithKline, and Actos (pioglitazone), made by Takeda, are both thiazolidinedione (TZD) drugs, already known to produce cardiovascular side effects. Both Avandia and Actos are known to increase the risk of heart failure and are required by the US Food and Drug Administration (FDA) to carry strong label warnings. In addition, Avandia increases the risk for heart attack, a finding that has caused its sales to plummet since the knowledge became public in May 2007.

Sonal Singh, of Wake Forest, and colleagues at the University of East Anglia, in Britain, found one additional bone fracture per 21 women age 70 and older, when TZDs were taken for one year. Younger women are at increased risk, too, with women around the age of 56 experiencing one additional fracture for every 55 women taking TZDs.

It is unknown at this time what causes the gender-specific increased risk for bone fractures but one theory suggests TZDs may interfere with the bone marrow’s ability to replace fat cells.