PTH and hyperphosphatemia: The acute reduction in our patient’s PTH from more than 1300 pg/mL to less than 20 pg/mL, effectively a non-detectable level consistent with near-complete parathyroid ablation, occurred in the setting of vigorous intravenous calcium replacement and persistent hyperphosphatemia with phosphorus levels of 6 to 8 mg/dL, creating calcium-phosphate supersaturation that most likely precipitated her CUA.