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Strontium Causes New, Heavier Bone Formation: Presented at ASBMR

By Em Brown

HONOLULU, HI -- September 26, 2007 -- The heavy metal strontium ranelate stimulates new bone formation and is preferentially taken up over calcium, resulting in new bone that is harder and heavier, researchers reported here at the 29th Annual Meeting of the American Society for Bone and Mineral Research (ASBMR).

Observational studies have previously shown that treatment of postmenopausal osteoporotic women with strontium ranelate reduces the risk of vertebral and hip fractures by 41% and 36% after 3 years, respectively.

In addition, biopsy results show that strontium-containing bones have the typical characteristics of normal bone, such as the presence of normal-shaped crystals, according to presenter Paul Roschger, PhD, Senior Scientist and Associate Professor, Ludwig Boltzmann-Institute of Osteology, Hanusch Hospital, Vienna, Austria.

To better understand the mechanism of strontium ranelate on bone, Dr. Roschger and colleagues at various site in Austria and Germany obtained biopsy samples from some of these trials, including the TReatment Of Peripheral Osteoporosis Study (TROPOS) and the Spinal Osteoporosis Therapeutic Intervention (SOTI) study.

The researchers analysed 3 years of data collected in 12 women who had been randomised to strontium ranelate 2 gm/day or placebo. They looked for strontium content in the biopsy samples using electron microscopy, x-ray microanalysis, and Fourier transform infrared microspectroscopy.

They found that bone samples from women on strontium ranelate had a higher atomic weight than the samples from women on placebo, which suggests that the heavier strontium ranelate replaced the lighter-weight calcium in the bone of women treated with this agent, Dr. Roschger reported.

X-rays also showed that the bone of women on strontium ranelate was very dense compared with those on placebo. Calcium's atomic number is 20, while the atomic number of strontium is 38, Dr. Roschger pointed out.

However, he added, "We can add strontium to bone, but we don't know how to normalise it. There is a lot we don't know about this drug.".

"Strontium was present exclusively in newly formed bone pockets, while older bone contained essentially no strontium," Dr. Roschger said in an interview. "Meanwhile, bone material characteristics were preserved -- the crystal size is the same as that of healthy bone."

However, he cautioned, "Heavier bones are not necessarily better bones -- they may be more brittle."


[Presentation title: Bone Material Characteristics in Osteoporotic Postmenopausal Women After 3-Year Treatment With Strontium Ranelate. Abstract S447]

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