Abstract
The parathyroid hormone has a key role in the regulation of the renal handling of phosphate (1, 2, 3), but it has become increasingly evident that other factors are, or may be, involved in this important homeostatic mechanism. These factors are primarily the pH, the extracellular volume, the circadian rhythm, dietary phosphate, steroids, diuretics, ionized calcium, calcitonin, and vitamin D.