Phosphate control of PTH secretion

Phosphate is not only one of the main components of the mineral phase of the bone, but it also plays many key biological roles. Its serum levels and balance are under the control of a great number of factors. In turn, phosphorus can control all these factors, through a complex network of mechanisms. Among these factors, PTH represents one of the main controllers of phosphorus metabolism, and phosphorus, in turn, has a manifold control of PTH itself, by both indirect and direct pathways. Though the indirect mechanisms through which phosphate controls PTH are at least in part well defined, the putative direct ones are by far less understood. There is sparse evidence that a system directly sensing phosphorus concentration is present in plants and unicellular organisms and probably also in some cellular systems of multicellular organisms (intestinal, renal, and bone cells), though it is not completely clear how they work. The possibility of the presence of such a phosphorus sensing mechanism has been hypothesized also for the parathyroid cells, suggesting many potential pathways, mainly based on experimental studies. However, it is still far from being definitively demonstrated.