PTH and Marchiafava-Bignami disease: As a result of PTH assay variability, preanalytical sample errors, and the phenomenon of end-organ PTH hyporesponsiveness, the 2017 KDIGO CKD-MBD guideline recommended the broad range for serum PTH targets (2–9 times the upper normal limit of the PTH assay) in patients with CKD G5D in order to reduce the risk of inducing adynamic bone disease.