Rare diseases of phosphate and calcium metabolism: Crossing glances between nephrology and endocrinology.

Rare diseases of phosphate/calcium metabolism correspond to a wide and heterogeneous spectrum of diseases. Recent knowledge in physiology and genetics has made it possible to better characterize them and to propose attractive therapeutic approaches based on the underlying pathophysiology. These diseases are often at the interface between nephrology and endocrinology. In this spirit of a multidisciplinary care, each specialty can bring its own critical point of view and its own specificities to improve patient care. The objective of this manuscript is to "read" with a nephrologist's point of view the main frameworks of diseases of phosphate/calcium metabolism, to illustrate the three crucial messages of nephro-protection sent to endocrinologists. First, calciuria must be interpreted both in absolute value (concentration hypercalciuria) and in ratio (flow hypercalciuria). Second, renal monitoring of therapies inducing hypercalciuria on kidneys with normal renal function (e.g. active vitamin D analogs or teriparatide) should be systematic. Last, hyperphosphatemia, often latent in hypoparathyroidism and pseudo-hypoparathyroidism, should be detected and at least benefit from dietary measures, in the context of Western diets rich in phosphate hidden in food additives.