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Higher vitamin D levels improves success of bone density drugs

Kathleen Blanchard's picture
Vitamin D and bone density drugs

Research now suggests higher than normal vitamin D levels are needed to ensure bone density drugs, known as bisphosphonates, are effective for preventing and halting the progression of osteoporosis.

The finding comes from Hospital for Special Surgery in New York. In their study, researchers found maintaining a circulating vitamin D level above 33 ng/m increases the success of bone drug density drug therapy seven-fold.

That number is above the upper limits of what the Institute of Medicine recommends for circulating 25-Hydroxy vitamin D levels.

Low vitamin D may explain failure of bone density drugs

Richard Bockman, M.D., Ph.D., chief of the Endocrine Service at Hospital for Special Surgery directed the study. He explains, "When you see a seven times greater effect” in the success of bisphosphonates, taken by 20 million people to improve bone health, “that is pretty impressive."

Dr. Bockman, who is also professor of Medicine in the Endocrine Division of Weill Cornell Medical College, notes a 20 percent response rate from the medications, and sometimes doubling of bone density, is discussed in medical literature, “but when you see a sevenfold improvement in outcome, you have to be impressed that it is probably important."

Bockman says 20 to 30ng/m of circulating vitamin D levels that the IOM says is adequate for normal healthy people, may not be enough for a favorable outcome for patients being treated for low bone mineral density (BMD).

Study is first to evaluate bone density drugs and vitamin D

The study is the first to formally study vitamin D levels and outcomes for improving bone mineral density and loss with the use of the FDA approved drugs alendronate, residronate, ibandronate and zolendronate.

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Research for the study consisted of a chart review of patients evaluated in an osteoporosis practice of Hospital for Special Surgery. Women included had been taking one of the four drugs BMD at least 18 months, were postmenopausal and had at least two bone mineral density scans 18 to 60 months away from the first scan.

Included were bone density T scores, history of fractures, calcium supplementation, body mass index and length of time of any of the four drugs used to treat or prevent osteoporosis.

Dr. Bockman explains how osteoporosis is identified by bone scans: "One standard deviation from the normal is a T score of one. Two standard deviations is a T score of two. Below the normal, it is a minus two and above the normal is a plus two. If your bone density is more than 2.5 standard deviations below the normal that defines a low bone mass that is considered to be osteoporosis."

The researchers also evaluated vitamin D levels at the time of bone scan and levels in between.

For the study, women responding to bone density drugs were considered those who had not sustained a fracture, less than 3 percent decrease in bone mineral density between the initial bone scan and follow up testing.

In the study that included 160 patients, 42 had decreased BMD. Twelve had a low T score that persisted and 17 sustained a fracture, making 71 of the participants unresponsive to bisphosphonate therapy – 54.9 percent of those had circulating vitamin D levels below 33 ng/ml.

Those with higher levels had a seven fold increased likelihood of successful treatment with the drugs designed to improve bone mineral density.

Vitamin D levels recommended by IOM may be too low for healthy individuals

Bockman notes there has been controversy about optimal levels of circulating vitamin D, but the American Geriatric Society, Endocrine Society, and the American College of Rheumatology either have vitamin D guidelines in place or are forthcoming that also are higher than 20 to 30ng/m.

The study, according to Dr. Bockman, shows vitamin D levels should be higher than that recommended by the IOM for anyone taking drugs to improve bone density for treatment and prevention of osteoporosis, but also suggests optimal levels for healthy people should be higher than Institute of Medicine recommendations.