PTH and Marchiafava-Bignami disease: With regard to markers of CKD-MBD, the serum Klotho level was positively correlated with the 1,25-dihydroxyvitamin D (1,25D) level (Figure 1C) and negatively correlated with the log intact parathyroid hormone (PTH) and fractional excretion of phosphate (FEPi) (Figure 1D, 1E).