TCN1 and chronic kidney disease: The proposed mechanisms to explain the association are that high vitamin B12 plasma concentrations may represent a response to increased release of vitamin B12 from liver storage, decreased clearance, upregulation of haptocorrin and transcobalamin synthesis, or diminished affinity of vitamin B12 for transporter proteins.1,3 Those situations are often present as a consequence of liver damage or CKD, which could be represented by the baseline association of high plasma concentrations of vitamin B12 with elevated concentrations of hepatic enzymes.