Purposes: The trabecular bone score (TBS) is an indicator of cancellous bone microstructure. A decrease in TBS is considered to be a risk factor for vertebral fracture that is independent of BMD. At the same time, it has been reported that, BMD was higher and TBS was lower in women with type 2 diabetes mellitus (DM), and a decreasing TBS is risk factor for fracture. However, the relationships between TBS and glucose metabolism indices in healthy people are unclear, and this study was conducted to elucidate these relationships.

Method: The subjects were 214 healthy postmenopausal women with HbA1c ≤6.2% who underwent an osteoporosis examination. On blood tests, fasting plasma glucose (FPG), HbA1c, Ca, P, Cr, PTH, 25-hydroxy vitamin D [25(OH)D], P1NP, and CTX were measured. Lumbar (L2-4) BMD and femoral neck (FN) BMD were measured with DXA, and TBS (L1-4) was calculated.

Results: The subjects’ mean values were age 63.2±7.5 years, BMI 22.7±3.0 kg/m², FPG 90±8 mg/dL, HbA1c 5.6±0.3 %, PTH 45.5±14.5 pg/mL, 25(OH)D 16.3±4.3 ng/mL, BMD (L2-4) 0.846±0.146 g/cm² (Z score 0.3±1.0), and FN 0.620±0.093 g/cm² (Z score 0.1±1.0). TBS was 1.317±0.073. An investigation of the correlation between TBS and each of these factors revealed that TBS was negatively correlated with age, PTH, and HbA1c, and significantly positively correlated with BMD, and 25(OH)D. On multiple regression analysis, TBS still showed a significant negative correlation with HbA1c even after adjusting for age, BMI and FN-BMD (r = -0.125, p < 0.05). The rate of the subjects with prevalent fractures was significantly higher in the group with higher HbA1c and lower TBS, compared to that of the groups with higher HbA1c and higher TBS.

Conclusion: These results suggest that very mild glucose intolerance, even within the normal range, may be associated with deteriorating cancellous bone microstructure in postmenopausal women.