His severe hypercalcemia was investigated with parathyroid hormone (PTH) that was appropriately suppressed to < 4 pg/mL (normal 10–65 pg/mL), PTH-related protein (PTHrP) that was not elevated at 0.9 pmol/L (normal ≤ 4.2 pmol/L), vitamin D 25-OH levels that were within a normal limit of 66 ng/mL (normal 30–80 ng/mL), vitamin D 1,25-OH levels that were also within a normal limit of 59 pg/mL (normal 19.9–79.3 pg/mL), and serum protein electrophoresis that showed no monoclonal protein. Here, PTH is linked to Hypercalcemia.