FGF23 and Marchiafava-Bignami disease: In fact, apart from measurement of 25(OH)D levels, required by 50/106 participants (47.2%) every 6 months, 35 (33%) every 3 months and 10 (9.4%) according to the values of calcium, phosphate, and PTH (Fig. 3A); only 27 clinicians (25.5%) consider determination of FGF-23 and Klotho to monitor the patients with CKD-MBD, while 67 clinicians (63.2%) never consider them (Fig. 3B).