Vitamin D in Dialysis Patients - Diagnostic and Therapeutic Management

The analysis will involve data obtained from medical records of dialysis patients who receive standard procedures consistent with national and international guidelines for specialized care. Specifically, we will analyze the levels of: * 25(OH)D, * 1,25(OH)2D * Calcium * Phosphates * PTH * FGF23 * GDF15 to assess the efficacy and safety of cholecalciferol in dialysis patients.