Type 2 diabetes mellitus is associated with increased axial bone density in men and women from the Hertfordshire Cohort Study: evidence for an indirect effect of insulin resistance?

AIMS/HYPOTHESIS: Previous studies have suggested that the high bone density often observed in type 2 diabetic patients may be explained by insulin resistance. We explored this hypothesis in the Hertfordshire Cohort Study. METHODS: A total of 465 men and 444 women aged 59 to 71 years and with no prior diagnosis of diabetes attended a clinic where a glucose tolerance test was performed and bone density measured at the femoral neck and lumbar spine. Biochemical markers of bone turnover (serum osteocalcin and urinary mean c-terminal cross-linking telopeptide of type II collagen) were measured in 163 men. RESULTS: According to WHO criteria, 83 men and 134 women were diagnosed with impaired glucose tolerance and a further 33 men and 32 women were diagnosed as having type 2 diabetes. Bone density was higher in newly diagnosed diabetic subjects, with relationships stronger in women (p<0.001) than men (p<0.05) and attenuated by adjustment for body mass index. In both sexes, we observed positive correlations between the total femur and femoral neck bone mineral density with measures of insulin resistance (r=0.17-0.22), with stronger results observed in women. These relationships did not apply after adjustment for body mass index. Glucose status did not lead to differences in osteocalcin level or c-terminal cross-linking telopeptide of type II collagen levels. CONCLUSIONS/INTERPRETATION: Our findings suggest that hyperinsulinaemia may affect bone mineral density through indirect effects, e.g. body weight.