Does size matter ?

(r1⁄4 0.495; P1⁄4 0.024). There were no relationships between IL-6 changes and the main mineral metabolism related parameters. Our results agree with previous experimental findings [4] and point to the efficacy of calcimimetic drugs for the control of uraemic SHP. It was unexpected that 6 months of cinacalcet treatment resulted in highly significant increases in OPG and decreases in Fetuin-A serum levels. OPG, a cytokine produced and secreted mainly by osteoblasts, has been claimed to play an as yet undefined role in the vascular calcification process. Although a protective effect of increased OPG levels on vascular calcification has been suggested, higher OPG serum levels have been linked to an increased extent of arterial wall calcification, increased mortality rates in uraemic patients, and most importantly, with increased mortality in dialysis patients [3,5]. The clinical significance of the OPG increase observed in our patients and its potential effects on the vascular calcification process cannot be drawn from our data. Interestingly, OPG increases were significantly correlated with the degree of reduction in c-Ca levels. In association with the OPG increases, cinacalcet treatment also caused significant decreases in Fetuin-A levels without changes in IL-6, indicating no change in the inflammatory state in our patients. The Fetuin-A reduction was significantly related to PTH decreases. Previous studies have emphasized an association between low Fetuin-A levels with both increased vascular calcification and cardiovascular mortality [2,6]. From our data, we cannot determine whether the Fetuin-A decrease represents a real increase in risk for the calcification process, or whether it is the consequence of a reduced demand for a feedback defence mechanism, which may be secondary to improved mineral metabolism, by cinacalcet, that reduces the pro-calcification burden. This possibility was proposed in non-dialysed diabetic nephropathy patients [7]. Although we are aware of the main limitation of this preliminary study, the highly significant changes in both OPG and Fetuin-A levels observed in our patients provide a stimulus and starting point for further research in this field.