Vertebral fracture risk in patients with differentiated thyroid cancer receiving TSH-suppressive therapy

BACKGROUND: Suppression of thyroid-stimulating hormone (TSH) can adversely affect bone tissue in individuals with differentiated thyroid cancer (DTC). This study aims to examine bone mineral density (BMD) and vertebral fractures (VFs) in DTC patients receiving levothyroxine (LT4) suppression therapy. METHODS: A total of 990 patients with DTC who had undergone total thyroidectomy and received levothyroxine suppression therapy for a minimum of one year were included in the study. Clinical and laboratory data obtained at the most recent visit were extracted from patient records. BMD measurements of the lumbar spine and femoral regions, assessed by dual-energy X-ray absorptiometry (DXA) within the preceding year, were recorded. When available, lateral vertebral radiographs were also evaluated. RESULTS: The study included 990 patients with DTC. According to DXA results, 545 (55.2%) had normal BMD, 363 (36.6%) had osteopenia, and 82 (8.2%) had osteoporosis. Osteoporotic patients were older and had lower BMI (P = 0.001 for both), while TSH levels were similar across groups. Among 476 patients with vertebral radiographs, 131 (27.5%) had moderate-to-severe VFs. Fracture rates were significantly higher in patients with severe TSH suppression compared with other groups (P = 0.013). Patients with VFs were older and had lower femoral neck and L1-L4 BMD (P = 0.001). Regression analysis showed that disease duration, FT4 levels, and femoral neck BMD were associated with fracture risk (P = 0.001). Multivariate analysis identified age, femoral neck BMD, L1-L4 BMD, and osteocalcin as independent predictors of osteoporosis (P = 0.001). TSH subgroups showed no differences in BMD values. CONCLUSION: Findings suggest that DTC patients undergoing TSH suppression have a significant risk of VFs. Assessments of VFs should be integrated into routine care for DTC survivors to ensure long-term skeletal safety.