Bone Abstracts

Treatment of postmenopausal osteoporosis with bisphosphonates reduces bone resorption and formation. Sclerostin, an osteocyte regulator of bone formation may be involved in these changes. Some studies have reported an increase in sclerostin associated with bisphosphonate treatment while others have reported a decrease. The aims were to determine the effect of bisphosphonates on i) circulating sclerostin and ii) PINP in postmenopausal women with osteoporosis. We studied 92 postmenopausal women with osteoporosis (<85 years) from a parallel group trial of bisphosphonates. They were randomised to receive ibandronate 150 mg/month (n=28), alendronate 70 mg/week (n=33) or risedronate 35 mg/week (n=31). They all received 1200 mg of calcium and 800 IU of vitamin D3/day. Fasting blood samples were collected at baseline (weeks −1 and 0) then at 1, 2, 4, 12, 13, 48 and 96 weeks and from 57 healthy premenopausal women (mean age 37 years) on one occasion. Serum sclerostin was measured by immunoassay (TECO Medical Group, Switzerland). The intra- and inter-assay coefficients of variation were 2.3 and 4.2% respectively. PINP was measured using an automated immunoassay analyser (the ISYS-IDS, UK). Median levels of sclerostin were significantly higher in postmenopausal than premenopausal women, 0.49 and 0.38 ng/ml respectively (P<0.0001), (Table 1). There was no significant change in sclerostin over the 96 weeks in any of the three treatment groups. There was a significant decrease in PINP by 67% (P<0.0001).