Calcium Receptor and Regulation of Parathyroid Hormone Secretion

The cloning of the CaR has made it possible to show definitively that the CaR is a critical mediator of the inhibitory effect of high Ca2+ on PTH secretion and parathyroid cellular proliferation. The receptor may also mediate the suppressive action of high Ca2+o on PTH gene expression, while its involvment in several other known actions of Ca2+o on parathyroid function remain to be examined. Alterations in CaR expression and/or function are clearly involved in hyper- and hypocalcemic disorders caused by inactivating or activating CaR mutations, respectively, and could contribute to the deranged Ca2+o-sensing in primary and uremic secondary HPT. Finally, CaR activators offer promise as the first truly effective mode of medical therapy for these latter two conditions.