Post-parathyroidectomy hypocalcemia: incidence, risk factors, and management

The purpose of this study was to evaluate the incidence and severity of hypocalcemia after parathyroidectomy and delineate its risk factors. Data was retrieved from a prospective database. Patients with postoperative hypocalcemia were identified and risk factors were investigated including primary versus renal hyperparathyroidism (HPT), preoperative calcium, parathyroid hormone (PTH) and alkaline phosphatase levels, gland weight, pathology, extent of surgery, and reoperative surgery. Of the 162 patients who underwent parathyroidectomy, 84 (52%) were hypocalcemic postoperatively: 55 (42%) of 132 patients with primary and 29 (97%) of 30 patients with renal HPT (P = 0.0001). Patients with renal HPT had more profound hypocalcemia with a mean +/- SD calcium of 7.34 mg/dL +/- 1.07 versus 7.76 mg/dL +/- 0.59 for patients with primary HPT (P < 0.05). Symptoms were present in 28 (51%) of 55 patients with primary and 13 (45%) of 29 patients with renal HPT. Only three (2%) patients with primary compared to 29 (97%) with renal HPT were treated with intravenous calcium. The average length of stay for hypocalcemic patients was 0.7 days for primary HPT versus 4.7 days for renal HPT (P < 0.0005). Patients with primary HPT who underwent subtotal parathyroidectomy had significantly lower postoperative calcium levels (7.95 mg/dL +/- 0.64) than patients who had a single or double adenoma removed (8.49 mg/dL +/- 0.79) (P = 0.036). No other factor was predictive of postoperative hypocalcemia. Patients with renal HPT develop profound postoperative hypocalcemia requiring intravenous calcium and vitamin D therapy. Hypocalcemia in patients with primary HPT develop less severe hypocalcemia that is amenable to outpatient oral calcium therapy and should be routinely initiated following subtotal parathyroidectomy.