PTH and chronic kidney disease: As correctly discussed by the authors, several in vitro and in vivo studies have suggested that indoxyl sulfate may play a part in the pathogenesis of low turnover bone disease as demonstrated by its effects on: (i) reducing parathyroid hormone (PTH) receptor expression on osteoblasts; (ii) inhibiting osteoclast differentiation and function; and (iii) reducing bone turnover in an animal model of CKD [2,3,4].