Role of deteriorated bone quality in the development of osteoporosis in pheochromocytoma and paraganglioma

Context: Pheochromocytoma (PHEO) and paraganglioma (PGL) (PHEO and PGL: PPGLs), catecholamine-producing tumors, represent an emerging cause of secondary osteoporosis. However, despite decreased bone mineral density (BMD), vertebral fracture (VF) is not associated with BMD in PPGLs. Objective: To evaluate whether deteriorated bone quality is involved in the development of osteoporosis in PPGLs. Participants: Trabecular bone score (TBS), used to assess trabecular bone quality, was examined in 56 patients with PPGLs and 52 with non-functional adrenal tumors (AT). Radiograph of the spine was carried out in 35 patients with PPGLs, and TBS was analyzed in 18 patients with PPGLs at follow-up. Main outcome measure: TBS and BMD at the lumbar spine in patients with PPGLs with and without VF. Results: PPGLs had a lower TBS (n = 56, 1.338 [1.294–1.420]) than non-functional AT (n = 52, 1.394 [1.342–1.444]; p = 0.033). Among those with PPGLs, patients with VF (n = 14, 1.314 [1.289–1.346]) had a lower TBS than those without VF (n = 21, 1.383 [1.324–1.426]; p = 0.046), despite no significant difference in BMD at the lumbar spine between the two groups (p = 0.501). An optimal cut-off level of TBS for diagnosing VF in PPGLs was 1.323, and its area under the curve was 0.702. The severity of catecholamine excess and maximal size of tumor were associated with decreased TBS in PPGLs patients (p = 0.016 and p = 0.020, respectively). Surgical resection of PPGLs improved TBS at follow-up, with 2.5% increase (p = 0.007). Conclusions: This study provides evidence for the importance of deteriorated bone quality rather than decreased bone mass in the development of VF in PPGLs.