Correlations between bone mineral density and circulating bone metabolic markers in diabetic patients

Diabetic osteopenia, a known chronic complication of diabetes, has been demonstrated with alterations in the calcium-vitamin D endocrine system. In order to investigate the relationship between the decrease of bone density and the altered mineral metabolism in non-insulin-dependent diabetes mellitus (NIDDM), 104 male clinical-proven NIDDM patients were studied. All patients were examined on metacarpal bone mineral density (m-BMD) by means of computed X-ray densitometry (CXD) methods. The values of the Z-score of m-BMD were significantly lower than those of age-matched controls (P<0.01). There was a positive correlation between m-BMD and serum calcium levels (P<0.01), but a negative correlation was conversely observed between m-BMD and serum intact parathyroid hormone (PTH) (P<0.01), indicating that the negative calcium balance under diabetic conditions could cause the decrease of m-BMD in NIDDM. Interestingly, since a significantly positive correlation was found between circulating levels of calcium and parathyroid hormone-related peptide (PTHrP) (P<0.05) but not PTH, it seems likely that PTHrP plays a more compensatory role on the maintenance of calcium homeostasis than PTH under diabetic conditions. Based on these observations, the CXD method would be useful in measuring the mineral density of cortical bone, and would also be beneficial to investigate underlying pathogenetic mechanism of diabetic osteopenia.