Long-term impact of teriparatide on bone mineral density, trabecular bone score, and fracture risk relative to total hip T-score: A two-decade, registry-based cohort study.

Background: Teriparatide followed by antiresorptive therapy exhibits fracture reduction efficacy for up to 2 years, but it remains unclear if this leads to sustained increases in bone mineral density (BMD) and trabecular bone score (TBS), and if BMD correlates with fracture risk reduction.

Methods: In this multicenter cohort study, the effect of teriparatide administration for 18-24 months, followed by antiresorptive therapy, was assessed in patients partipicipating in a nationwide Swiss osteoporosis registry. BMD and TBS were measured up to 10 years before and after teriparatide initiation.

Results: A total of 624 patients (87 % female, age 67 ± 13 years) were enrolled from May 2004 to December 2023. Among them, 198 (32 %) received no treatment prior to teriparatide, while 426 had received previous antiresorptive therapies (median duration 5.9 years [2.2, 8.0]). All patients underwent subsequent antiresorptive therapy, mainly with bisphosphonates and denosumab. The incidences of vertebral, hip, and any fractures were 0.96, 0.11, and 1.37, respectively, within 2 years prior to teriparatide initiation. The total hip T-score did not correlate with fracture reduction under teriparatide. After transitioning from teriparatide to an antiresorptive regimen, fracture incidence remained low and BMD was significantly higher for up to 5 years after teriparatide compared to the pre-treatment period (T-score + 0.876 for lumbar spine, p < 0.001; and + 0.112 for total hip, p < 0.005), while TBS increased by 0.047 (p < 0.001). Overall, significant improvement was observed in pretreated and treatment-naïve patients undergoing teriparatide treatment.

Conclusions: Teriparatide led to sustained lower incidences of vertebral, hip, and other fractures for up to 8 years after switching to antiresorptive agents in both pretreated and treatment-naïve patients. Additionally, BMD and TBS levels were significantly higher than those before teriparatide treatment. During teriparatide treatment, the total hip T-score did not correlate with fracture risk.