Low TSH Levels Within Euthyroid Range Could Play a Negative Role on Bone Mineral Density in Postmenopausal Women with Type 2 Diabetes

OBJECTIVE: We aimed to evaluate the relationship between thyroid-stimulating hormone (TSH) and bone mineral density (BMD) in euthyroid type 2 diabetes (T2D). METHODS: This retrospective analysis enrolled 439 T2D patients with normal thyroid function, including 226 males and 213 females. All the female patients were postmenopausal. Serum glycosylated hemoglobin A1c (HbA1c), TSH, free triiodothyronine (FT(3)), and free thyroxine (FT(4)) concentrations were analyzed. BMD of the lumbar spine (L(1)–L(4)), femoral neck, and hip joint was determined using dual-energy X-ray absorptiometry. RESULTS: The patients were grouped based on tri-sectional quantiles of the TSH levels: 0.55~1.70mIU/L (Group 1), 1.71~2.58mIU/L (Group 2), and 2.59~4.74mIU/L (Group 3). Our data showed that, in male patients, no difference in BMD was identified among groups. In postmenopausal women, unlike at the lumbar spine (P = 0.459), the mean BMD at the femoral neck (P = 0.014) and hip joint (P = 0.014) had a statistical difference among groups and increased with TSH level. In addition, our analysis demonstrated that TSH levels shown no correlation with BMD at all sites in males. However, in females, BMD at the femoral neck (r = 0.156, P = 0.023) and hip joint (r = 0.172, P = 0.012) had a positive correlation with TSH levels. After adjusting for age and BMI, multiple regression analysis showed that TSH levels influenced BMD at the femoral neck (β = 0.188, P = 0.001) and hip joint (β = 0.204, P = 0.001) in female patients. CONCLUSION: In summary, our data demonstrates that low TSH levels are associated with decreased BMD at the femoral neck and hip joint in postmenopausal T2D women with euthyroidism.