PTH and rickets: The phosphaturic action of Fgf23 has been very well documented, and excessive circulating intact FGF23 actually leads to hypophosphatemia and rickets or osteomalacia.20, 21 Therefore, it is currently a conundrum why profoundly elevated serum levels of intact Fgf23 post‐MI do not translate into hypophosphatemia and hyperphosphaturia in the presence of unchanged serum PTH, the other major phosphaturic hormone.