PTH and chronic kidney disease: According to the CKD–MBD guidelines (Chiang, 2017; Ketteler et al., 2017; Baptista et al., 2020; GBD Chronic Kidney Disease Collaboration, 2020; D'Arrigo et al., 2022), i-PTH, a polypeptide hormone produced and secreted by parathyroid chief cells, plays an important role in bone metabolism, and plasma calcium and phosphorus concentrations need to be monitored in adult patients at the beginning of stage 3 CKD.