PTH and Marchiafava-Bignami disease: These results imply that serum 25(OH)VitD3 concentration should be measured when eGFR is <60 mL/min/1.73 m2, to identify individuals who might benefit from PTH suppression therapy for secondary hyperparathyroidism and CKD-MBD as well as vitamin D supplementation, although further large-scale studies, in particular of individuals with CKD stages 3 or 4, are warranted.