"Trabecular Bone Score" (TBS): An indirect measure of bone micro-architecture in postmenopausal patients with primary hyperparathyroidism

Background: Patients with primary hyperparathyroidism (PHPT) generally show reduced bone mineral density (BMD) at cortical sites with relatively preserved trabecular bone. However, the increased fracture risk at all skeletal sites suggests that areal BMD probably is not effective in capturing all the determinants of bone strength. "Trabecular Bone Score" (TBS) has been recently proposed as an indirect measure of bone micro-architecture. Our study was aimed to investigate TBS in patients with PHPT. Methods: Seventy-three Caucasian postmenopausal women with PHPT and 74 age-matched healthy women (C) were studied. In all participants BMD at lumbar spine (LS) and at femoral sites (Neck-FN and total hip-TH) was measured by DXA and, in 67 patients and 34 C, also at the distal 1/3 of the radius (R). TBS was measured in the region of LS-BMD. Spine X ray was assessed in all patients. Results: Mean TBS values were significantly reduced in PHPT (1.19 ± 0.10) compared to C (1.24 ± 0.09, p. <0.01). Patients and controls did not differ for age, years since menopause (YSM), BMI, 25(OH)D serum levels, creatinine clearance, LS-BMD and FN-BMD. On the contrary, mean BMD values at both TH and R were significantly lower in PHPT patients compared to controls (p <0.01 and p <0.0001, respectively). In PHPT with vertebral fractures (VF. +, n = 29) TBS was significantly lower than in those without fracture (VF. -, n = 44)(1.14 ± 0.10 vs. 1.22 ± 0.10, respectively; p <0.01), whose TBS values did not differ from C. Mean TBS values in patients with (n = 18) and without (n = 55) non-vertebral fractures did not significantly differ (1.16 ± 0.09 vs. 1.20 ± 0.11). The presence of vertebral fractures was independently associated with the reduction of TBS (OR = 0.003, 95% CI = 0-0.534, p = 0.028) and with YSM (OR = 1.076, 95% CI = 1.017-1.139, p = 0.011), but not with age, the reduction of LS-BMD and the increase of BMI. The combination of YSM > 10. years plus TBS <1.2 was associated with a significant risk of VF (OR = 11.73, 95% CI 2.43-66.55, p <0.001). A TBS value <1.2 showed a better performance in individuating VF (sensibility 79.3%, specificity 61.4%, positive predictive value 57.5%, and negative predictive value 81.8%) in respect to YSM > 10. years. Conclusions: TBS seem. s to indirectly reflect an alteration of bone micro-architecture in postmenopausal women with PHPT.