[Calciotropic hormones and integrated regulation of calcemia and calcium balance].

Calcium homeostasis is regulated by fluxes occurring at the levels of bone, kidney and intestine, fluxes which are controlled by calciotropic hormones. Bone resorption is stimulated by parathyroid hormone and by the bioactive metabolite of vitamin D, 1,25-dihydroxyvitamin D, or calcitriol. The renal tubular capacity to reabsorb calcium is regulated by parathyroid hormone, and calcium intestinal absorption is increased by calcitriol. Any modification of extracellular calcium concentration triggers a series of hormonal homeostatic reactions, aimed at changing these fluxes and correcting thereby calcium homeostasis perturbations. The evaluation of these fluxes provides information on the pathophysiological mechanism(s) implicated. Then the determination of calciotropic hormones circulating levels allows one the confirmation of the diagnosis evoked.