1.
Renal Phosphate Reabsorption is Correlated with the Increase in Lumbar Bone Mineral Density in Patients Receiving Once-Weekly Teriparatide.
Takeuchi, Y, Kuroda, T, Sugimoto, T, Shiraki, M, Nakamura, T
Calcified tissue international. 2016;(2):186-92
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Abstract
In order to assess the changes in serum calcium and phosphate and the changes in renal tubular phosphate reabsorption (TmP/GFR) and to evaluate the association between these indices and the increase in bone mineral density (BMD) with once-weekly intermittent administration of teriparatide (TPTD), the results from the teriparatide once-weekly efficacy research (TOWER) trial were re-analyzed. The TOWER trial studied postmenopausal women and older men with osteoporosis. Patients were randomly assigned to receive TPTD 56.5 μg or placebo for 72 weeks. Of these patients, the present study investigated those whose calcium and phosphate levels and lumbar BMD (L-BMD) were measured (TPTD group, n = 153 and Placebo group, n = 137). The TPTD group had significantly lower serum phosphate, calcium-phosphate product, and TmP/GFR at weeks 4, 24, 48, and 72 and urinary fractional calcium excretion (FECa) at weeks 12, 48, and 72 (p < 0.05). In the TPTD group, the serum phosphate and TmP/GFR during early treatment (4, and 12 weeks) showed a significant positive correlation with the percent change in L-BMD at weeks 48 and 72. Based on multivariate analysis corrected for age, BMI, and L-BMD at the start of treatment, serum phosphate and TmP/GFR at week 4 showed a significant correlation with the percent change in L-BMD. This study suggests that the L-BMD response to once-weekly long-term TPTD treatment is associated with circulating phosphate or with the status of its renal reabsorption. Preventing decrease in serum phosphate levels may be important in acquiring greater L-BMD with once-weekly TPTD.
2.
Higher response with bone mineral density increase with monthly injectable ibandronate 1 mg compared with oral risedronate in the MOVER study.
Nakano, T, Yamamoto, M, Hashimoto, J, Tobinai, M, Yoshida, S, Nakamura, T
Journal of bone and mineral metabolism. 2016;(6):678-684
Abstract
We examined response to bone mineral density (BMD) gains in the MOVER study following treatment with intravenous (IV) ibandronate 1 mg/month, and investigated the characteristics of a non-responder group. At 1 year, responder rates for patients with BMD increases >0 % were similar with IV ibandronate 0.5 or 1 mg/month and oral risedronate 2.5 mg/day. However, after 3 years, responder rates with BMD increases ≥3 % were highest with ibandronate 1 mg at all bone sites (>80 % at the lumbar spine [L2-L4] and >50 % at all femur sites, which was significantly higher than with risedronate). Non-responders were defined by BMD increases ≤3 % at L2-L4 or ≤0 % at total hip, and ≤50 % reduction in creatinine-corrected urinary collagen type 1 cross-linked C-telopeptide (uCTX) from baseline to 1 year. There were a small number of non-responders in the ibandronate 1 mg group: 3.3 % (10/299) with ≤0 % total hip BMD increase and ≤50 % uCTX reduction from baseline. These non-responders had lower 25-hydroxyvitamin D (25[OH]D) levels than responders, but no differences in kidney function, L2-L4 BMD or bone turnover marker baseline values. Throughout the study, non-responders failed to show any increases in BMD. Our analysis demonstrates significantly higher responder rates with IV ibandronate 1 mg/month than with risedronate at 3 years. A small number of non-responders in the ibandronate group had lower 25(OH)D baseline levels than responders, suggesting that 25(OH)D levels could be a useful indicator of BMD response to therapy.