FIGURE 4:

Pathophysiology of secondary hyperparathyroidism in CKD. Initially in SHPT, the parathyroid glands grow diffusely with polyclonal parathyroid cell proliferation (diffuse hyperplasia). At this stage, VDRAs activators and calcimimetics are effective in lowering PTH concentrations. Afterward, cells in the nodules are transformed monoclonally and proliferate. In parallel are four patterns of parathyroid hyperplasia: diffuse hyperplasia, early nodularity in diffuse hyperplasia, nodular hyperplasia and single nodular glands. In the advanced stages of SHPT, downregulation of calcium sensing receptor (CaSR), VDR and Klotho-FGFR 1 makes parathyroid cells resistant to the inhibitory effect of calcimimetics, calcitriol and FGF-23.