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.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.Mean TBS values were significantly reduced in PHPT (1.19 ± 0.10) compared to C (1.24 ± 0.09, p 10 years plus TBS 10 years.TBS seems to indirectly reflect an alteration of bone micro-architecture in postmenopausal women with PHPT.