PTH and Marchiafava-Bignami disease: Furthermore, Bolignano et al., previously demonstrated that Cathepsin-K, a lysosomal cysteine protease secreted by activated osteoclasts and promoting bone and extracellular matrix remodeling, was associated with PTH levels, in a setting of 85 chronic hemodialysis patients, suggesting that this protein could represent a biomarker of CKD-MBD severity and PTH levels [76,77,78,79,80].