PTH and chronic kidney disease: In another longitudinal cohort study, Nickolas et al. found that patients on CKD experienced progressive loss of cortical density and thickness along with increased porosity in the bone, which were driven by increased bone turnover based on PTH and bone-specific ALP levels; the authors also found that PTH and bone-specific ALP levels predicted the decreases in the cortical area (2.2% and 2.8%, respectively).