PTH and Marchiafava-Bignami disease: In addition to its effects on these diseases, it is also likely to have a beneficial effect in CKD-MBD, because the active form of vitamin D, 1,25(OH)2VitD3, suppresses serum PTH concentration both directly and indirectly, through the vitamin D receptor in cells of the parathyroid gland and an increase in serum Ca, respectively (14).