Background: Vitamin D regulates calcium and phosphate absorption in the small intestine as well as bone mineralisation. Our objectives were to describe the correlations of serum 25(OH)D with the serum and urinary calcium, phosphate and creatinine, the serum iPTH and β-crosslinks, as well as with the bone density (BMD) in type 2 diabetes patients on oral antidiabetic drugs.
Methods: One hundred type 2 diabetes patients participated 56 men and 44 women. The mean age and diabetes duration of the women was 59 and 9.8 years, of the men 58 and 7.7 years, respectively. None of them was taking calcium / vitamin D supplements or antiresorptive treatment. Serum levels of 25(OH)D were measured as 25(??)D Total, iPTH by an electro-hemi-luminescent method and β-crosslinks by ECLIA (all three on an Elecsys 2010 analyzer, Roche Diagnostics, Switzerland); serum and urinary calcium, phosphate and creatinine - on a Cobas Integra analyzer. Hip BMD was measured on a GE Lunar Prodigy Pro bone densitometer (GE Healthcare, Madison, WI). Correlation analysis was performed on a SPSS 13.0 for Windows platform (SPSS Corp., Chicago, IL) and included 10 curves. The data were first analysed for the group as a whole, then separately for men and women and for vitamin D tertiles.
Results: Serum 25(OH)D was correlated with serum calcium and phosphate (R2=0.417 and R2=0.389, p<0.001), as well as with urinary calcium (R2=0.091, p=0.03), but not with iPTH, urinary phosphate, creatinine or β-crosslinks. The correlation with BMD was of borderline significance. The sub-analyses according to gender or 25(OH)D tertiles did not add useful information.
Conclusion: In type 2 diabetes serum vitamin D has an impact on serum calcium and phosphate but not on their urinary excretion. iPTH, β-crosslinks and BMD are subject to more complex regulation and the relative contribution of vitamin D is hard to prove.
Disclosure: The authors declared no competing interests. This study was sponsored by the Scientific Council of the Medical University of Sofia, Bulgaria; Grant no. 60/2011, Project no. 46.