GC and acute respiratory distress syndrome: 25(OH)D3 circulates tightly bound to the VDBP (also known as Gc-actin).18 VDBP levels were 40 mg/dL in normal controls, 19 mg/dL in ARDS and 28.7 mg/mL in the at-risk patients at the beginning of oesophagectomy (figure 4).