Risk factors for postthyroidectomy hypocalcemia

Hypocalcemia is a common complication of thyroidectomy. The aim of this study was to evaluate the incidence of hypocalcemia after thyroid operation and its relation to clinical, biologic, and surgical factors.

A retrospective study of 265 patients who underwent unilateral (n = 50) or bilateral (n = 215) thyroidectomy between 1996 and 2000 was done to determine incidence and risk factors for hypocalcemia. Free thyroxine and thyrotropin levels were obtained before operation in 254 patients, together with preoperative and postoperative calcium and phosphorus levels. All patients were examined for age, gender, extent of thyroidectomy, initial versus reoperative neck operation, pathologic characteristics of resected thyroid tissue, substernal thyroid extension, and parathyroid resection and autotransplantation.

Hypocalcemia, defined as a calcium level less than 2 mmol/L, occurred in 42 of 265 patients (16%), including 11 (4%) symptomatic patients who required vitamin D, calcium, or both for 2 to 6 weeks. Factors significantly predictive of postoperative hypocalcemia in univariate analysis included elevated free thyroxine level (p = 0.0064), bilateral thyroidectomy (p = 0.00064), parathyroid autotransplantation (p = 0.0128), and female gender (p = 0.0028). Independent risk factors on multivariate analysis were elevated free thyroxine level (p = 0.0476), bilateral thyroidectomy (p = 0.0338), and parathyroid autotransplantation (p = 0.0003).

Bilateral thyroidectomy, elevated free thyroxine level, and parathyroid autotransplantation are independent risk factors for postthyroidectomy hypocalcemia. Oral calcium supplements may be of value in this group of patients to enhance early hospital discharge.