Calcium-sensing receptor (CaSR), allosteric agonist on parathyroid

Class

Calcimimetic (peptide agonist)

Pathway

Parathyroid hormone (PTH) / calcium-sensing receptor axis

Notes

original target text: Calcium-sensing receptor (CaSR), allosteric agonist on parathyroid chief cells

The calcium-sensing receptor (CaSR) is a G protein-coupled receptor expressed on parathyroid chief cells, where it functions as the body's primary sensor of extracellular calcium concentration. When blood calcium rises, CaSR activation suppresses release of parathyroid hormone (PTH), the hormone that mobilizes calcium from bone, kidney, and intestine. In chronic kidney disease, phosphate retention and disturbed vitamin D metabolism drive parathyroid chief cells to secrete excessive PTH, a condition called secondary hyperparathyroidism, which over time causes bone disease and abnormal calcification of blood vessels and soft tissue. A calcimimetic is a molecule that binds CaSR at a site distinct from calcium itself, allosterically increasing the receptor's sensitivity to circulating calcium. This makes chief cells behave as though calcium levels are higher than they actually are, lowering PTH secretion without requiring a rise in serum calcium. This mechanism offers a way to control PTH output directly at its cellular source, complementing approaches that manage phosphate or vitamin D. It broadly matters wherever parathyroid hormone excess threatens bone integrity or vascular health, particularly in patients with impaired kidney function undergoing dialysis.