In women taking rosiglitazone, bone resorption was up 33% while bone formation held steady.

SAN FRANCISCO—The culprit in rosiglitazone-associated bone thinning may be increased bone resorption, according to new data presented here at the annual meeting of The Endocrine Society.

In a recent study, investigators found that women with type 2 diabetes taking this agent had a higher rate of fracture.

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In addition, some short-term studies (12-14 weeks) measuring the effects of rosiglitazone showed decreases in such bone formation markers as procollagen 1 N-terminal propeptide (PINP), osteocalcin, and bone-specific alkaline phosphate. Until now, there have been no double-blind, randomized studies in a multi-ethnic cohort that examined the effects of longer-term use of this agent on bone formation and resorption markers in type 2 diabetics.

Researchers at the University of Texas Southwestern Medical Center (UTSMC) in Dallas studied 111 pa-tients (66 men and 45 women) with type 2 diabetes who participated in the Dallas Heart Study. The study group included 50 African Americans, 18 Hispanics, and 37 Caucasians, as well as individuals of other ethnicities. All subjects had a history of CVD or were older than 40 years and had at least one CVD risk factor.

In this six-month study, participants were randomized to receive either placebo or rosiglitazone 4 mg/day for one month and then 8 mg/day for five months. The primary end points of the study were changes in PINP and carboxy-terminal cross-links (CTX).

Women who took rosiglitazone for six months had a 33% increase in bone resorption (based on CTX), but no changes were observed in bone formation (as measured by PINP). The increase in resorption occurred regardless of age. The researchers observed no change in bone resorption or bone formation markers in men.

“We were surprised by these findings,” said study investigator Ugis Gruntmanis, MD, associate professor of medicine at UTSMC and chief of endocrinology at the VA North Texas Health Care System in Dallas. “When we went into the study, we thought it would support published data that rosiglitazone decreases bone formation.” 

Women taking rosiglitazone must be aware that this drug can make bones thinner and that bone density must be checked prior to starting this drug, Dr. Gruntmanis said.