Bone Microarchitecture and Fracture Risk in Differentiated Thyroid Cancer Patients Undergoing Long- Term TSH Suppressive Therapy

Purpose Recent management strategies for differentiated thyroid cancer (DTC) have shifted toward less conservative and individualized therapeutic approaches. Nevertheless, long-term thyroid-stimulating hormone suppressive therapy (TST) remains indicated for patients at high risk of persistent or recurrent disease, and its long-term skeletal impact has not been fully defined. This study aimed to assess clinically available bone health parameters in women with DTC who underwent prolonged TST. Methods In this cross-sectional study, 103 women with DTC (41 premenopausal and 62 menopausal) were evaluated. Forty-eight patients received TST for more than five years, and 55 received TST for less than five years. Bone mineral density (BMD), trabecular bone score (TBS), bone turnover markers, vertebral fractures, and FRAX-estimated fracture risk were systematically assessed. Results Menopausal women had significantly lower BMD and TBS values than premenopausal women (p < 0.001 and p = 0.035, respectively). Degraded bone microarchitecture was more prevalent in menopausal patients (60%, p < 0.001). Although degraded microarchitecture occurred more frequently in patients receiving long-term TST than in those treated for ≤ 5 years (50.0% vs. 27.8%), this difference was not statistically significant (p = 0.064). In contrast, among menopausal women, long-term TST was strongly associated with degraded TBS (55.6% vs. 16.7%, p < 0.001). Bone turnover markers did not differ between the groups. FRAX® analysis indicated a higher estimated risk of major osteoporotic fractures in menopausal women receiving long-term TST, whereas the hip fracture risk was predominantly driven by menopausal status. Conclusion These findings underscore the importance of proactive bone monitoring in patients with DTC receiving prolonged TST, particularly in menopausal patients. TBS and TBS-adjusted FRAX® provide complementary information beyond BMD and support individualized long-term risk stratification and therapeutic decision-making processes.