editore: Springer International Publishing AG
Vitamin D deficiency, circulating levels lower than 15 ng/ml, is an epidemic disease worldwide with more than a billion people suffering of it in the beginning of the 21-century. Besides its impact on mineral and bone metabolism, these low vitamin D levels are also associated with a diversity of non-skeletal complications, among them cardiovascular disease, diabetes mellitus, multiple sclerosis, cancer, tuberculosis, and immune system dysfunction. Chronic Kidney Disease is also a very common disease, affecting more than 10% of the world population, ranging from stage 1 to stage 5 before dialysis. Approximately 1% of the population in industrialized countries is affected by end-stage renal disease (ESRD), needing a renal replacement therapy either hemodialysis or peritoneal dialysis, and ultimately by renal transplantation. Those CKD patients are more susceptible to exhibit reduced vitamin D stocks. Consequently, more than eighty percent of CKD patients have either insufficient or deficient vitamin D levels for multiple reasons.