Sub-group analyses
To investigate whether the severity of vitamin D insufficiency would influence the results, we performed subgroup analyses in patients with S-25(OH)D levels below or above (and equal to), respectively, the median level of baseline S-25(OH)D (56 nmol/L) of the 85 patients that completed the study (depicted in Table In the subgroup of high 25(OH)D levels, all markers of erythropoiesis decreased significantly over time within the treatment group, and TSAT decreased by a trend (We also assessed whether patients on the higher range of S-HEP-25 (> 4,8 nmol/L) levels would exhibit a greater decrease in hepcidin markers as compared to the PBO group. However, none of the markers of hepcidin, erythropoiesis, or iron availability, changed more over time as compared to the PBO group (data not shown) even though the H/F ratio decreased over time within the VD group (from 47 (32–73) to 45 (25–56); 