Bone quality, as measured by trabecular bone score in normocalcaemic primary hyperparathyroidism

Background: The impact of normocalcemic hyperparathyroidism (NHPT) on bone quality remains largely unexplored. We aimed to investigate the usefulness of trabecular bone score (TBS) assessment in NHPT and the accuracy of TBS in predicting vertebral fractures (VFs) in NHPT. Methods: In this multicentric cross-sectional study, we assessed the TBS in 47 subjects with NHPT, 41 with primary hyperparathyroidism (PHPT) and 39 age- and sex-matched control subjects. Results: TBS values did not differ among the three groups. The prevalence of low TBS (TBS<1.2) was 23.4% in NHPT, 26.8% in PHPT and 15.4% in controls, without statistically significant differences between groups. However, we found a lower Lumbar spine Z-score adjusted for TBS (LS Z-score*TBS) in PHPT participants when compared with controls (-0.48 ± 1.06 vs 0.07 ± 0.93, p: 0.017). In NHPT group, LS Z-score*TBS did not detect patients with overall VFs (Threshold -0.15, AUC 0.45 95%CI 0.253-0.648, accuracy 55.3%). Instead, it was useful for moderate-severe VFs (Threshold 0.55, AUC 0.81, 95%CI 0.62-0.996, accuracy 83%). In PHPT subjects also, TBS did not predict VFs. Conclusion: In NHPT, TBS is not reduced. When adjusted for TBS, the LS Z-score might predict moderate to severe VFs.