Comparative effects of denosumab or bisphosphonate treatment on bone mineral density and calcium metabolism in postmenopausal women.

Objectives: To clarify potential differences between denosumab (DNS) and bisphosphonates (BIS) in terms of bone density and bone metabolism, in a sample of postmenopausal women.

Methods: A total of 113 postmenopausal women aged 53-66 years were treated with either DNS or BIS for 12 months. Bone densitometry and laboratory tests were compared between baseline and follow-up.

Results: Femoral neck BMD increased in both treatment-arms (FN-BMD, DNS: 0.69±0.07 g/cm to 0.75±0.09 g/cm; BIS: 0.69±0.06 g/cm to 0.71±0.07 g/cm; p≤0.001 in both cases). Lumbar spine BMD (LS-BMD) increased significantly only in the DNS-group (0.83±0.14 g/cm to 0.89±0.14 g/cm, p=0.0001). Only women under treatment with DNS had a significant increase in serum parathyroid hormone (PTH: 44.87±17.54 pg/mL to 53.27±15.77 pg/mL, p=0.04), independently of baseline vitamin D levels. DNS-administration resulted in higher increase from baseline in FN-BMD compared to BIS (DNS vs BIS: 8.7%±8.5 vs 3.8%±7.3, p=0.004). Finally, baseline 25OH vitamin D levels did not determine the extent of PTH-increase following administration of DNS- or BIS-treatment.

Conclusions: Both treatments increased BMD, however, the effect of DNS on FN-BMD was superior compared to that of BIS. DNS-treatment increased serum PTH. Baseline 25OH vitamin D levels did not predict the extent of PTH increase at follow-up.