Change in Bone Mineral Density with Strontium Citrate: An Illusion or Reality

Abstract

Case 1 76-years-old female with OP took alendronate weekly for 10 years till 2006, then every other week for another year and was initiated on a drug holiday. She started self-administrating SrC (680mg/day) in 2006 and continued to take daily calcium (600mg bid) and vitamin D (2000units). Serum calcium and Vitamin D (32-66ng/ml) remained normal. She continued SrC on her own till 2012, when she agreed to stop taking it due to concerns about accumulation and toxicity. On Dual Energy X-ray absorptiometry (DEXA) scan, total hip mean BMD increased 2.7% in the first 2 years on SrC after stopping alendronate, and continued to increase to a maximum of 9.2% after 6 years of treatment with SrC (1.53%/year). Lumbar Spine (LS) BMD was nondiagnostic due to degenerative changes in the spine. In the first 2 years off of SrC, total hip mean BMD decreased by 5.7%. Case 2 64 year old female with history of osteoporosis, which was diagnosed in 2001. She took Actonel 35mg weekly for 5years, stopped for more than a year and resumed Actonel intermittently for another 2 years before starting drug holiday. She was taking Calcium 500 mg in the multivitamin and 2500 mg of vitamin D. Serum calcium and vitamin D were within normal range. She started strontium citrate 680mg daily in 2009 and took it for 5 years, stopping it in 2014. Yearly assessment of her BMD via DEXA scan showed an increase of 4.3% at LS spine (L1-L4 vertebrae), and 7.6 % at total hip within 1 year of SrC treatment. At 5 years, BMD increase was 6.5 % at LS and 12% for mean total hip. She agreed to stop SrC at this time. 1 year after stopping SrC, LS BMD decreased by 9.1 % and total hip BMD decreased by 4.2%. Case 3 59 year old female with OP was treated with weekly alendronate for 4 years till 2007, when she stopped it due to concerns for osteonecrosis of jaw. She was advised to resume alendronate in 2008 due to declining BMD, but opted not to take it. Abstract We are seeing an increased use of Strontium Citrate (SrC) as a nutritional supplement in the US in the form of self-administration by patients to improve bone density. There are no current data available on the effectiveness and safety of SrC on bone. Strontium Ranelate (SrR) is used to treat osteoporosis in Australia/Europe but is not FDA approved in the United States (US). Sr is a heavy element and when incorporated in the bone can cause overestimation of BMD. We report an increase in Bone Mineral Density (BMD) in three patients with osteoporosis who took over the counter SrC. After stopping SrC, all of them were noted to have a significant decrease in BMD. These findings suggest that the increase in BMD with SrC may be a result of accumulation of Sr in the bone, and the decrease in BMD after its discontinuation may be related to lower Sr levels in bone. In the absence of data on the efficacy and safety of the effects of SrC on bone and the technical interference of Sr on BMD measurement, it may be safer to avoid using it. Further studies are needed to delineate the effect of SrC on bone health and safety.