The regulation of calcium homeostasis involves the interaction of several “calciotropic"
hormones with multiple organs. Recent work suggests that ex-tracellular calcium itself
functions as a calciotropic hormone, in that it acts via a cell-surface receptor to regulate
cellular processes. Here we discuss the molecular mechanism of this “calcium sensing” and
review how disruptions of a molecular calcium sen-sor can cause abnormalities of calcium
metabolism in humans: familial hypocalciuric hypercalcemia, neonatal severe …