Low Normal TSH Levels and Thyroid Autoimmunity are Associated with an Increased Risk of Osteoporosis in Euthyroid Postmenopausal Women

Background and Objective: Studies on the relationship of thyroid stimulating hormone (TSH) within the reference range and thyroid autoimmunity with osteoporosis have produced conflicting results. The objective of this study was to investigate the association of thyroid function and thyroid autoimmune bodies (TPOAb and TgAb) with osteoporosis in euthyroid postmenopausal women. Methods: A total of 174 subjects were retrospectively included. Serum TSH, total T3, total T4, TPOAb, TgAb, vitamin D, calcium and bone mineral density were measured. Correlation and logistic multivariate regression analysis were performed. Results: Levels of TSH were lower in osteoporosis group (TSH: 2.03±1.08 vs 2.40±1.24 mIU/L, p=0.040) while TT3 and TT4 levels were similar between the two groups. The positive percentage of anti-TPO antibodies was higher in osteoporosis group (17.9% vs 6.7%, χ²= 5.13, p=0.024) while no significant difference was observed for anti-Tg antibodies (17.9% vs 8.9%, χ²=3.05, p=0.081). The Spearman correlation analysis showed that TSH levels were significantly correlated with lumbar spine BMD (r= 0.161, P=0.035) and femoral neck BMD (r = 0.152, P= 0.045). Logistical regression analysis revealed that low-normal TSH levels and positive TPOAb was an independent risk factor for osteoporosis (OR: 0.698, 95% CI: 0.505-0.965, p=0.030; OR: 3.961, 95% CI: 1.176-13.345, p=0.026 respectively). Conclusion: The results showed that low-normal TSH levels and anti-TPO antibodies were independently associated with the presence of osteoporosis in postmenopausal women.