Fig. 8
From: Phosphate acts directly on the calcium-sensing receptor to stimulate parathyroid hormone secretion
Pi is an important regulator of CaSR activity. In health, CaSR negatively modulates PTH secretion to control Ca2+ homeostasis. An acute rise in Pi inhibits the CaSR and would permit increased PTH secretion which stimulates renal Pi excretion to help restore normal serum Pi levels. However, in the hyperphosphatemia of CKD, the additional Pi would stabilize the CaSR’s inactive conformation permitting chronically elevated PTH secretion and contributing to SHPT progression. CaSR-ECD crystal models obtained from PDB 5k5s (active) and 5k5t (inactive) and shown as surface. Created with Biorender.com
