After the stage 1 osteotomy, severe hypercalcemia (peak: 3.79 mmol/L; reference: 2.11-2.52 mmol/L) and elevated PTH (995 pg/mL; reference: 15-65 pg/mL) emerged, leading to Single-photon emission computed tomography (SPECT) confirmed diagnosis of a left inferior parathyroid adenoma. The gene discussed is PTH; the disease is Hypercalcemia.