*4.2.2.2 VD and infection*

Infection is a well-recognized leading cause for death in CKD patients, especially those on dialysis. It was already mentioned that the VD axis plays a role in immunity by enhancing cathelicidin production. In dialysis patients, low cathelicidin levels were detected, which were associated with higher risk for infection and also modest correlation to 1,25VD levels was discovered [52]. Interventional studies also demonstrated the decreased risk for infection in dialysis patients. VD supplementation reduced significantly the risk for hospitalization due to acute respiratory infections in hemodialysis (HD) patients; in another study, VD supplementation decreased the risk for peritonitis in patients on peritoneal dialysis (PD) [53, 54]. A more recent study also demonstrated decrease in infection rates in dialysis patients treated with VDR analogs [55]. In contrast to these findings, Yildirim et al. failed to demonstrate a significant relation between VD status and inflammatory markers in CKD patients [56].

### *4.2.3 VD pleiotropy in CKD: neoplasia*

An already mentioned paper demonstrated reduced malignancy-associated mortality in VDA-treated dialysis patients. However, the study did not evaluate the specific localization of the neoplasia, nor its histology [55]. Therefore, in this subsection, the most common malignant diseases will be reviewed and their association with VD. Unfortunately, the exact association between VD and neoplasia in CKD patients is not well evaluated, as CKD patients are usually excluded from large trials and registries [57].

#### *4.2.3.1 Breast cancer*

The reports evaluating the association between VD deficiency and breast cancer are inconsistent. The inverse association between breast cancer and VD, detected in several studies was not supported by more recent prospective studies. In addition, a controversy exists about the beneficial effect of VD supplementation on breast cancer risk and survival [44]. Unfortunately, the cited studies did not demonstrate data for CKD patients.
