To study the possible mechanisms whereby vitamin D deficiency worsens with increased severity of liver dysfunction, we measured hydroxylases protein levels of CYP2R1, CYP27A1 (key enzymes in vitamin D synthesis) and CYP24A1 (key enzyme in vitamin D degradation) in 94 out of 345 subjects (Table 4). The gene discussed is CYP27A1; the disease is Decreased liver function.